Window Trim Tools, Materials and Terminology

The interior trim work on your windows can help define the feeling and ambiance of a room. Whether you are trying to achieve a very stark modern look, or looking for rich, deep and heavy feel, the woodwork that you choose and the way you install it will play a large role in the overall finished appearance of your home.

Before we begin talking about how to create each style and which type of trim might be best for you application, let's take a quick look at the tools and materials that you'll need to have on hand to do the job correctly.


  • Miter Saw: This is the one tool that you absolutely cannot do without when doing any kind of finish carpentry. A miter saw will allow you to cut angles and bevels with pinpoint accuracy. The fastest and most accurate way to do this is with a power miter saw, but if you are trying to save some money or just like the nostalgia of doing things the old fashioned way, then you can use a miter box with a hand held saw. This is a lot more work, but it will allow you to get the job done.

  • Coping Saw: This is a small hand held saw that is used to cut small pieces away from the beveled ends of trim pieces. It is specifically used when creating cornice pieces and turn backs on your apron.

  • Finish Nailer: This tool is a nail gun that is powered by an air compressor or a battery and a gas cartridge. You can do the job with a hammer and a nail set, but this is much faster.

  • Hammer: You are going to need a hammer even if you are using a pneumatic nail gun. You may need to pull pieces away to make adjustments, and you may need it to use with a nail set to sink nails that the gun doesn't drive all the way in.

  • Nail Set: This small tool is vital in finish carpentry. Use it to drive nail heads below the surface of the wood so that the hole can be filled.

  • Jig Saw: This will be used to cut in the horns on your stool. (Don't worry if you're not sure what those are, we'll cover it below.)

  • Table/Circular Saw: A table saw is ideal. You will need to use this to rip your stool to the correct depth. The table saw is a faster, easier, and more accurate tool to use when making rip cuts. A circular saw will work if you don't have access to a table saw, but it can be a pain.


  • Nails: If you have access to a nail gun, then you'll need to check the specs on the gun to know what size and brand of nails to buy. Make sure that they are at least 1 1/2" long.

  • Finish Nails: If you are going to be using a hammer and a nail set to install your window trim, you will need to buy a box of #6d finish nails. Make sure that you don't buy the galvanized kind, as these are meant to be used outside.

  • Trim: After choosing the style you want to use, you will need to determine the material. If you are planning on painting your trim work, then a finger jointed or fiberboard molding will be more economical and will look just fine with two coats of paint. If you are planning on staining and varnishing your woodwork, then you will need to select the wood species that you want to use. Pine and oak are the two most popular, but some other species can be purchased or ordered through specialty retailers.

  • Level: You will need a level to make sure that your head, sill, and side casings are level.

  • Tape Measure: Make sure you have one that measures small increments - at least 1/16".

  • Marking Tool: I always have a pencil stuck in my ear. An ink pen can leave marks on your wood that will bleed through paint later on.

  • Wood Putty: This will be used to fill nail holes and ensure that your finish, whether paint or stain, is smooth and professional.

  • Sandpaper: Keep a few sheets of 150 grit paper handy to smooth out the wood putty when it dries.

A Glossary of Window Trim Terms

Before we begin with specific instructions, let's lay out some of the basic terms that we will need to use in order to get the job done. Some of these may be new to you:

Apron: The decorative piece of trim that runs right underneath the stool.

Stool: The stool is often mistakenly called the sill. Remember, the sill is always on the exterior of the window. The stool actually rests on top of the inside edge of the sill and extends into the room.

Sill: The sill is the bottom portion of the window frame that is visible from the outside. The bottom sash rests on the sill.

Head Casing: This is the piece of trim that goes across the top of the window.

Miter: A joint that is formed by putting together two pieces of wood that have been cut to form a pre-determined angle, usually 90 degrees.

Butt joint: A butt joint is formed when the flat edges of two pieces of wood are placed together to form a joint.

Horn: The outside edges of the stool, where it wraps around the window frame, are called the horns.

Reveal: A reveal is the amount of overlap that is allowed to show underneath a piece of trim.

Sill Casing: When using a wrap-around trim style, this is the piece of trim that goes along the bottom of the window.

Side Casing: The trim that runs along each side of the window.

Continue to Part 2: Installing the Trim >

Brian Simkins is a freelance writer living in Chicago. He enjoys using his 14 years of home improvement experience to educate and equip new home owners.