Doors – Looking for name of door trim part

A router (along with a special guide) can be used to cut part of the inset you need, but is not the easiest tool to use if you are not experienced, and it does not cut square corners, which still require a chisel to finish.

Using a chisel does take care and practice, but it is not beyond the reach of even an amateur if you are willing to do a test piece first and then go very slowly.

You need to draw the opening with a sharp pencil (or and awl). Many people use a utility knife to cut the outline to slightly deeper than needed, then use a small, sharp chisel, following the grain of the wood (in this case toward the top and bottom, not across the door) taking very thin layers out until you are deep enough.

It does not need to be perfectly flat at the bottom of the channel, just the right depth at the ends with no high spots in between.

If you practice on a scrap of wood first, you may be surprised that you can do it.

Rubber air seals along the bottom will be your best bet. An automatic bottom seal may work slightly better, but its a very slight difference over a properly installed gasket seal.

Make sure your door is perfectly balanced in the frame before installing a gasket. You need to make sure the gap is uniform across the entire bottom of the door.

Foam tape would work just as well across the top and sides, and may be cheaper depending on what bottom seal you choose.

Its worth mentioning, unless you have an inch or more gap, its unlikely this extra gap-seal is going to solve the underlying issue. So much of the sound is still going to be transmitted through what are most likely uninsulated interior walls. Soundproofing tends to be a project that just keeps going.