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Casing Doors: Part 1

The trim that surrounds a door frame is called casing, and it’s always installed before baseboard and chair rail because they have to butt against it. Casing is also the easiest type of molding to install because the joinery is simple, making it a perfect first project.

I’ll start off by explaining the details of casing joinery and describing how to measure for new casing around a door frame. I also talk about making a cut list, so when you cut your casing it will be perfect the first time.


Chapter 2: Part 1

A serial publication of excerpts from Trim Made Simple by Gary Katz

Training techniques for apprentice carpenters and serious DIYers


Most trim carpentry revolves around using a miter saw. In this article, I’ll introduce fundamental techniques for cutting correct miters in casing—techniques that I’ll build on in later articles for baseboard, chair rail, and crown molding. I’ll demonstrate a simple system for cutting casing that will help you cut each piece of molding to exactly the right length—every time. In future articles, we’ll use elements of the same system for cutting other types of trim.

Before installing new casing, the old molding must be removed, without damaging the wall or the jamb. I’ll cover the best and simplest tools and techniques for that job, too. Then I’ll demonstrate two ways for installing moldings: the time honored one-piece-at-a-time method, and a new way of pre-assembling casing that ensures tight miters and a neat job. By the end of part 2 of this story, you’ll be able to install new casing with confidence.


Installing casing is not only the easiest trim carpentry chore but requires the least amount of tools. Buy good quality tools. Good tools work better and last longer.

Utility Knife for cutting loose old casing
Spring clamps for assembling perfectly tight and flush miters
Trim Gauge for marking exact reveals on jambs
Wire cutters for removing old nails from a jamb or wall
5-in-1 tool for prying casing loose from a wall, and scraping old caulking off the jamb and wall
Prybars for removing old casing from a jamb and wall (they work best in pairs)
Nail sets for setting nails just beneath the surface of the casing
Thumb Saver for starting small nails in molding without hammering your fingers
Dovetail saw/backsaw for cutting baseboard back when the new casing is wider than the old molding
Multimaster for cutting baseboard back when you’re installing casing on more than 10 new doors
Nail gripper for driving hand nails without hammering your fingers or the molding


Three 7-ft. pieces of 2 1/2-in.-wide casing in a “3-step” profile pattern, made from fingerjointed, unprimed wood
Carpenter’s glue for tight, long lasting joinery
Nails (nail gun) for fastening the molding to the jamb and wall

Understanding Casing Joinery

Before tackling any new job, make sure you see the whole picture. Casing can be confusing. A quick drawing is often the best solution, especially when it comes to miters. Miters are angled cuts, so they always have a short point, where the length of the material is shortest, and a long point, where the length of the material is longest.

Some carpenters refer to the short point as the “heel” of a miter, and the long point as the “toe,” which is another way of understanding the angle of a miter. Because casing surrounds the outside of a door frame, the short points matter most: The short points of the miters are always on the jamb, on the inside edge of the casing, near the door. For casing, all measurements are taken to the short points.

(Click any to enlarge. Hit your browser’s “back” button to return to this article.)

Cutting Casing

Avoid frustration. Always make cut lists for moldings. That’s the best way to ensure a smooth enjoyable job. With cut list in hand, you can confidently head for your saw; without one, you will likely find yourself in front of the saw trying to remember a crucial measurement, and then heading back to measure again. And with a cut list, you’ll always know which way to miter your moldings—without closing your eyes and trying to remember the room you just left.

Make a Cut List

1. Measure the head first. If the old casing isn’t on the jamb, measure the inside of the jamb (inside dimension, or I.D.) and then add 1/2 in. for 1/4-in. reveals on both sides of the jamb.
2. Measure leg casings. Press the tape measure hook into the floor, pinch it at mid-height against the door, then stretch and curl the tape up over the top of the jamb. Measure to the inside of the jamb and add 1/4 in. for a reveal.
3. Make cut list. Write down the measurement for the head and label it HEAD. Write the measurement for the right leg and label it RH; write the measurement for the left leg and label it LH.

. . .


Please don’t try anything you see in THISisCarpentry, or anywhere else for that matter, unless you’re completely certain that you can do it safely.

. . .

Leg Casing

At first, cutting miters in casing is confusing. To make the job easier, always place casing with the back edge against the miter saw fence. That way, the long points of the miters will always be against the fence, and the short points of the miters—and all the measurement marks—will always be nearest to you, where you can best see them. With the measurement marks away from the fence, it’s easy to guide the saw blade right to the mark, which you’ll see when you cut the casing legs.

Cutting the legs

1. Cut the legs first. Place one piece of casing on the left side of the saw. That will be the left-hand leg. Place another piece of casing on the right side of the saw, that will be the right-hand leg.
2. Measure up from the bottom. Hook your tape measure on the bottom of the casing, stretch the tape up towards the saw, and make a measurement mark on the font edge of the casing. Do the same for the opposite leg.
3. Cut the right-hand leg. Swing the saw towards the right to 45 degrees. Place your right hand at the end of the miter saw fence, wrapping your thumb around the casing. Position the measurement mark about one inch from the blade and make a practice cut.

4. Look from front of saw. Sighting down the saw blade is the hardest way to align the blade with the measurement mark. The measurement mark is easier to see from the front of the saw, even with the blade spinning. With your thumb wrapped around the casing, slide the casing toward the blade, creeping the measurement mark forward until the blade cuts right on the mark.

5. Cut the left-hand leg. To cut the left leg, swing saw to left. Place your left hand at the end of the miter saw fence and wrap your thumb around the casing. Make a practice cut, wide of the measurement mark, then creep the measurement mark up to the blade.

Head Casing

Always cut the head casings last because you can cut them from shorter pieces (sometimes from legs that you mistakenly cut too short!). The head casing is a little trickier to cut because both sides have miters. A simple technique makes it very easy to cut double miters at exactly the right length.

1. Miter right end. Clamp the casing to the end to the miter saw extension table, with the short point flush with the edge. Hook your tape measure on the edge of the miter saw table, then pull the measurement.
2. Measure with a sharp pencil. Use a no. 2 1/2 lead pencil for a sharp, fine line. Never round off fractions. Always make measurements exactly, to within 1/32 in., which is a little more or a little less than the nearest 1/16 in. mark on the tape measure.
3. Make a practice cut. Hold the casing with either your right or left hand placed at the end of the miter saw fence. Wrap your thumb over the front edge of the casing. Make a practice cut about 1/2 in. away from the measurement mark.
4. Creep up on measurement mark. The more you use a miter saw, the closer you’ll make your practice cuts and the fewer practice cuts you’ll make. But don’t rush the learning process. Cutting right on the measurement mark is what matters most.

Cut Casing with a Miter Box

Hand-powered miter boxes work well for cutting small moldings, as long as you use a good one. But no matter what type of saw you use, a miter saw stand and continuous support for your material is essential.

1. Clamp your workpiece. When using a miter box, be sure to clamp the material securely to the table and to the tool. That’s the only way to ensure a perfect miter.

2. Let the saw do the cutting. Too much pressure on the saw will distort the miter cut. Never “try” to make a miter saw cut. Allow the saw to cut by itself. Pull the blade smoothly and gently backwards across the molding. Use light pressure to push the saw forward. Move your arm slowly back and forward as if it were a machine.


Keep an eye out for Part 2 of “Casing Doors,” coming soon from THISisCarpentry!


51 Responses to “Casing Doors: Part 1”

  1. Al

    Very surprised to know of the existence of those two “thumb savers” tools.
    All these years going to HD almost on a daily basis and never saw anything like that on the shelves.
    Or I was completely missing it?
    Thanks for the pictures.

    • Gary Katz

      Oh get out of here, Al! That was a suggestion for beginners and DYI’ers who don’t have nail guns! You can also use a small scrap of cardboard and stick a nail through that if your fingers are too big. :)

  2. David Bailey

    I like the idea of the nail gripper and the thumb saver. I don’t believe the nail gripper exists as a product any longer though. Any other manufacturer producing a similar item?
    My DeWalt chop saw doesn’t look anywhere near as new as yours pictured here.
    Thanks Gary
    Dave Bailey

    • Gary Katz

      Not you TOO! :)

      My DW saw is a collectors item now. It has very low mileage. I know they are not built for longevity–not at that price, so I don’t drive it much.

  3. Ryan Mulkeen

    Thanks Gary. Very well thought out and presented, as always. Any tips on adding backbands? The rabbet measurement always seems to throw me off.

    • Gary Katz

      Cutting backband molding is very much like cutting rabbeted panel molding except for backband you’re cutting to the short point (just like casing windows and doors). While with rabbeted panel molding you’re often cutting to the long point. Either way, the difficult part is compensating for the rabbet because you can’t see the “real miter” and you have to measure to the “false miter.”

      Make sure the inside of the molding—the rabbet—is pointing toward you, so you can see your short point measurement. When you measure the piece, SUBTRACT the size of the rabbet from the shortpoint measurement. You may have to make a test cut to determine the exact amount to subtract so that the cut passes precisely through on the “real miter”.

      • Ryan

        Thanks Gary – I greatly appreciate the diagram as well – pictures always help to pull it all together.

  4. Kreg mcmahon

    Nice article and very informative for beginners and pro’s alike thanks ! Kirk I am surprised you use your comb In case you broke off a tooth on the comb your hair won’t be just right!

    • Kirk Grodske

      Hey Kreg,

      Nylon combs don’t break. It may have been a while since you tried one, what with the bandanas and all. :)

  5. Rich Cargin


    For cut list paper I like to use drywall paper. We always have some in the van for it’s intended purpose. It’s tough, cheap, fits in the pouch and it’s available on most job sites.

    I rip off a 12″ piece and fold it twice. That gives me many different sides to write on.


  6. John Bunday

    I actually approach this a little diffferently. After the material is delivered to the job I select the best pieces for the long legs and rough cut the others for the head casings. I then cut the LH miter on the head casg. with the saw swung to the right. IE the long point of the head casg. pointing to the right on the chop saw. After marking the reveals on the jambs, I then hold the head casg. in place and mark the RH miter directly from the jamb lay out. By so doing, you can then cut the RH miter on the saw and see exactly where your cut mark is. Now fasten the head place. Next cut a right and left miter on 2 side pieces and hold them miter cut DOWN against the floor and tick mark the exact length at the top of the installed head casg. Square cut the sides to length and install. If you are installing the trim before the finish floor has been installed and you know the thickness of the flooring you can cut a spacer block to gauge the amount needed to shorten the sides.
    Another invaluable widget I use to record measurements and notes while working is a round mylar disk available from Fastcap that sticks to the face of your tape measure. You can write dimensions, notes, or even make a small sketch and when done simply wipe away your scribbles and proceed to the next assignment.

  7. J.E. Thiessen

    Interesting to read a step by step breakdown of a common job. You might get better stock in your area than I do, but I’d add a step right at the beginning to cut the bottom of the leg jamb clean and square before tackling the miters.


  8. Greg DiBernardo


    You are really the master at breaking down technical processes and illustrating them. Nice work…AGAIN!

    While this article is probably a little rudimentary for most of us, I can tell you that I’ve found it never hurts to revisit something even as basic as this because usually, we get stuck in our ways and stop picking up little tricks.

    The little tricks are what separates us from the novice.

  9. Mark Parlee

    Good article

    I do as you do. This is very production oriented and works well. It also leaves enough to trim the miters to the correct angle if you need to throw them slightly off.

  10. Larry

    I’ve never been on a job where the drywall and jamb were even. You are really lucky to have that level of framing and drywall installation. Here to compensate we either shim the molding while cutting or use a block plane to do a slight back bevel. The wider the molding the worse it gets. On larger moldings, expensive houses, we are now providing pre-assembled casings. They are held together with Hoffmann keys. Cutting on a high quality miter saw in the shop also helps. We use an Omga, very nice saw. Since most all of my work is now shop based I’ve never actually installed the pre-assembled casings but have made a lot of them for contractors. They are usually prefinished also. I suspect some fooling around with the drywall bumps is required on site. We are currently running 9 1/2″ base and 6″ casing for an older house restoration. Miters were not used on this size casing. The head casing has 5 different moldings used and most have returns.

    • Marko

      This was also a problem in my house. It would also be interesting to hear Gary’s advice on this.

      • Gary Katz

        Larry is absolutely right. On most jobs, the drywall is proud of the jambs. That’s because standard jamb stock for interior walls with 1/2 in. drywall is only 4 9/16 in. wide; for 5/8 in. drywall, the jambs come 4 5/8 in. wide. That can NEVER work. We order all of our interior jambs 4 3/4 in. wide. Problem solved. Same with window jambs. We add an extra 1/8 in. to all exterior wall thickness measurements (drywall, sheathing/shear, studs, etc). On jobs where we don’t have that kind of control, the first thing I do is sent a helper around the house with a 12″ piece of casing, a pencil, and a big hammer. He holds the casing FLUSH with the inside face of jamb, scribes a pencil line along the back of the casing all the way around the opening, then beats down the drywall, coming up to the line but not crossing it. Then, when the casing slides back 1/4 in. for the reveal, all the damage is hidden. If the condition is reversed, we plane the jamb with a power planer and an 1/8 in. strip of scrap taped to the bottom sole of the plane, so you don’t cut into drywall and the jambs stay 1/8 in. proud. If the drywall is more than 1/8 in. proud of the jamb (or maybe 3/16? or maybe 1/4 in just a few places…this is really a seat of the pants call…we’ll cut jamb extensions. Sometimes that the easiest thing to do…just swallow and to it right from the start. Of course, that helper sweeps every room as soon as he’s done, otherwise the finish guys (me) have to work in a mess of drywall scraps and dust. I hate that.

        If you want me to send you that helper, let me know. :)

  11. Steve Christopher

    Hi Gary,
    Nice article on trimming.
    Don’t know if you are familiar with these.
    They have a thin edge with a long tapering profile that gets behind molding without causing the dents in drywall or molding made by thicker bars.
    The off brand clones have a chisel type ground edge, so make sure you get Hyde.
    Also the hook end gets the built up paint off the reveal area on the edge of the jamb.

    • john Bunday

      Around here we call this A “Bee Tool” since their original purpose was to open and scrape honey out of a bee hive.
      That being stated, one of these guys has lived in my tool pouch for over twenty years. Incredibly handy for scraping, prying, back scratching, and opening paint cans.

  12. Alex

    I’m glad to see an article like this, I grew up in this trade and I am always eager to see how someone else performs a task. Great job.

    I notice that you place your length mark on the face of the casing, I have started to find that as my eyes have gotten older and on some profiles a mark on the inside edge of the casing makes it easier to see and let’s me be a little more accurate. I also wonder if anyone has opinions about the larger saws for cutting trim. I find that my large dewalt really requires a premium blade for acceptable results but they seem to be the saw of choice on most jobsites. I also have a 7-1/2″ makita that seems to cut great with a pretty inexpensive blade. Any body else? I suspect it has something to do with how the larger blade flexes at high rpm, but I really haven’t tested my theory.

  13. Kenny B

    Gary, thanks for making me a better carpenter and thanks for your articles.

    After attending your roadshow several years ago, I started gluing up all of my miters with the miter clamps. This has really been working great for me, but the main issues I have cutting and gluing up so many miters is 1) having to constantly switch the miter to LH & RH cuts and 2) either not having enough clamps or floor space for gluing.

    I have found it beneficial to start cutting the head casing after cutting my first leg angle (be it LH or RH) and then finish the head casing after switching angles for the other leg.

    Granted I have the potential for an extra “goof” leg left over from the job, but I can start gluing up my joints sooner and not be left running out of floor space (or clamps).

  14. gary

    What is the value of gluing up end grain miters? I would think the painter would have quite a time with any squeeze out on a stain job. How are you dealing with drywall that recedes from the jamb? I notice you didn’t use a compound miter in your procedure. Will that be shown in your next issue?
    I enjoy your articles and hope to attend a “roadshow” one day.


    • Gary Katz

      I know. You’d think the end-grain miters wouldn’t hold with glue, but they do, especially if you apply real pressure to the joint. Jim Chestnut taught me that. And Franklin Glue confirmed it. If you don’t apply any real clamping pressure, the glue will only provide about 15-20% of its real strength. That may be why you’ve never had much luck with glued miter joints?
      And for stain-grade jobs, gluing the miters is especially important–it helps seal the end grain. If you don’t seal the end grain, the stain will wick right into the miters and you’ll end up with a dark line right on the miter–which doesn’t look so swell. That can happen on splice/scarf joints, too, like in baseboard or crown, which really looks terrible.
      As for removing the glue, yes, that’s important, especially on stain-grade material. A damp rag or toothbrush comes in handy when you’re working with stain-grade wood. Check this out:

  15. Owen Sechrist

    Good Article

    For production paint grade trim jobs where new doors and jambs are installed I always go around and make a list of all the head measurements from short point to short point and number each door where the casing will cover.

    I get a count of right and left legs and a leg length.
    I set the bevel of my saw(~3 to 4 degrees) and adjust the mitre less than 45 (usually about 44.5 degrees) to give me a backcut on the mitre. Then I’ll cut a left leg and hold it up to a door to double check (critical step!!) I then set a stop on my saw stand and cut all my left legs rapidly using the stop/jig.

    Repeat the process for the right legs.

    For my heads I don’t usually backcut them, but if you want to backcut them cut all the head pieces to a length just beyond your long point to longpoint measurement.

    Then you can set your bevel and mitre and make all the left end cuts, then reset it to make all the right end cuts.

    For the lengths on the head casings, usually you are repeating a measurement, so once I have one of a certain length cut I set the back edge of the casing against the back edge of the next piece and use the long points to mark the next piece of the same length.

  16. Tom Bainbridge

    we clearly all approach this slightly differently

    my casing cut list is written left to right, always
    one line is one door side, always

    i cant miss a measurement and the number on the left of the line is always the left leg, the centre is the head…………..

    if its just a single door i take a casing set to the door and mark them off

  17. Dave Cotter

    I have a question about gluing miters and priming. So if I’m priming all sides, including the two surfaces of the miter before install, especially with exterior trim, will this weaken the glue joint? I suppose this is a more general question as well about whether the paint film of primer will affect the strength of glue joints.



    • Gary Katz

      Actually, you shouldn’t prime the miters or any joinery that you intend to glue–I mean, the joinery you cut first. The glue join will be much stronger if it’s raw wood. When you glue to the primer or paint, you’re relying on the adhesion of the paint to the wood. When you glue directly to the wood, the glue penetrates the wood fibers. Glue can also be used to seal the endgrain, which is why you need to spread glue evenly on both ends of a miter.

  18. jonathan

    Currently, in michigan it seems like there are not many custom jobs happening (that i am aware of), and it seems like you have to get an excellent product (installing the molding) in the fastest time possible. What do you think is the fastest way to get the most casing up? I was introduced to the miter spring clamps, and I just mark my reveals on the jambs, put my casing up to the jambs and mark the intersecting points, and premake all my casing with the spring clamps, let them dry and then install them all at once. Do you think there is a faster way? The same with base molding, do you think its faster to measure all your rooms, cut them all, then install, or do them piece by piece?

    • Gary Katz

      I think that with wider casings, it’s much faster and you get a much nicer job by pre-assembling the casings. I still make a cut list and work as productively as possible at the saw, cutting all the legs, and then the heads, so I’m cutting long lengths first and getting all the shorts out of what is left, plus my saw stand and repetitive stops are setup for long lengths first and then 2/6, 2/8, and 3/0 heads (after the 4/0 and 5/0 heads are cut!).

      Baseboard is the same. I believe in making a cut list for ONE room, cutting, fitting, and installing those pieces, and then cutting the next room.
      Same with Crown. One room at a time.

  19. John

    Thanks! Another great article Gary. Why aren’t you using your Kapex? Your review of it convinced me to buy one. I love it.

  20. Joe Dunn

    After watching your glowing review, my wife allowed me to retire my Dewalt DW718 and run (not walk) to get a Festool Kapex. Now, I see you back with a DeWalt. Say it ain’t so.
    Joe Dunn

    • Gary Katz

      The reason for the DeWalt is pretty simple. I wrote that book for Fine Homebuilding and they said they wanted to market it at big box stores. They asked me to use tools that were available at those types of stores. Since my motivation for doing all the shows and books and articles is to teach techniques, it didn’t matter ‘that’ much to me which saw I used…sort of. I had just gotten my first Kapex when I started that book and wanted to use it, but. I guess in some ways it’s like working on a house with a tight budget. You want to install a two piece mahogany cornice but all they can afford is mdf crown.

  21. Marko

    One question to Gery. Have you ever used a miter trimmer? It’s a cutter with two sharp blades.

    I’m figuring if it would be an option for me because it does not spread dust as a miter saw (first I cut the trim with a simple mitre block).

      • A W Smith

        In the eighties that’s all we had were miter trimmers. Well that and those back saws and boxes. Chop saws were just coming out and few of us had them. There were two that we used, a Dosch which was German made and cut beautifully. And a lion which was just about identical but didn’t hold an edge as well. You would creep up on the mark and if you wanted a back cut you flipped the casing over and peeled off a sliver. I loved working with Miter trimmers. We left the job with not much sawdust but little piles of cheese curls lying around LOL.

  22. Rich Kocher

    If my right leg and left leg are plumb and parallel, I will flip my head piece upside down and face toward the wall and mark the head casing at the toes of the left and right casings. Cut the 45’s on the outside of the marks and drop into place. If ok, glue, clamp and affix.

  23. Kasey

    Where did you get the 3 step casing in your article? Is there an online supplier?

    • Gary Katz

      Yes, don’t you like that profile? It’s so simple and yet so elegant. Proves the point about over-dressing a molding.

      You can get that profile through most dedicated molding suppliers. And any good mill shop probably has that knife and can cut you the molding without a knife charge. WindsorONE makes a similar 3-step profile, though the back is cut square and would have to be detailed for a casing, or a backband applied. I really like the WindsorONE profile because the fillets are cut extremely sharp. It has great ‘punch’.

  24. Mike Hawkins

    Hi Gary,
    good articles as always. I go one step further and pre-assemble my door casings with glue and spring clamps. I do the same with windows if they are being picture framed. I use Titebond III and find that it sets up enough in 20 minutes, enough to move the casing assy with care. I mark all my reveals ahead of time and take measurements for each piece then cut them all. By the time I’m done glueing up the assemblies, the first ones are ready to go.
    Mike Hawkins

  25. Laurie

    I’ve done a little woodworking but I’m mostly a beginner. We have a home with unfinished open doorways and I would like to finish them. Here’s a dumb question – how do you finish the inside of the doorway? I don’t intend on putting doors in them. So do you first add wood to the inside of the doorway frame and then calculate the casing measurements? Would any kind of wood do for the inside? What thickness would you suggest? Thanks!

    • Gary Katz

      I’m not sure what type of openings you have right now. If they’re drywalled, then yes, you can either install a wood ‘jamb’ and then case the jamb, or you can remove the drywall and then install a wood jamb. Either way, installing a jamb is always the first step.

  26. Dani Rojo

    Hey Gary!

    Love the article! I was wondering where you got the casing? We just moved into a new home and they have it but I cannot seem to find it anywhere!

    Thank you so much for your help!!

    • Stephen Jones

      Realize this is a rather old thread but did you get an answer to location to purchase the casing? I have “3-step” profile pattern in my home as well and cannot find it anywhere.
      Thanks for the help!

      • Gary Katz

        That molding is available at any professional molding store and through most progressive lumberyards. It’s extremely common. However, WindsorONE makes the very nicest 3-step molding, and look for the Colonial Revival Apron), though it has a square edge on the back–which makes it a nice baseboard. To use that molding at casing, you’d have to ease the back edge with a router and 1/8 in. or 3/16 in. round over bit.

  27. Lala

    Hi where did you buy the “3-step” casing and base molding in your demos? I’ve been looking for it to match a 1920’s home in unprimed wood but not seeing any manufacturers online.

  28. Staan watowich

    Hello – We are finishing a remodeling project and need to replace some of the current door/window casing, which matches the 2 1/2-in.-wide casing in a “3-step” profile pattern shown in this article. Does anyone know where I can purchase this casing?

  29. apkDirect

    Great post, Paul! I’ve been struggling with casing doors properly for years. Your step-by-step instructions and photos are very helpful. I’m looking forward to Part 2 to see how you finish the job.


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