In addition to the things Ken mentions, some builders use card stock or heavy paper, even thin goatskin; basically anything that doesn't have grain like wood -- or if it does, you run the grain at right angles to the wood grain.  I've also seen builders saturate the wood with glue on the underside of the top to harden it up

updated by @ken-hulme: 03/05/21 05:03:18PM

Bill, a lot of it depends upon the design. Some folks put a thin piece of wood under the sound hole area with the grain running perpendicular to the top grain and then cut out the hole. A friend of mine saves used dryer sheets and glues that in the area where the sound hole will be cut out. Others glue small pieces of wood around the hole to keep cracks from developing.

Ken

"The dulcimer sings a sweet song."

I'm totally ignorant of instrument design, Bill, so I can't help you.  But if you don't get good answers here, you might consider joining the Dulcimer Making Group and asking your question there.

--
Dusty T., Northern California
Site Moderator

As a musician, you have to keep one foot back in the past and one foot forward into the future.
-- Dizzy Gillespie
updated by @dusty: 03/05/21 04:40:32PM

I have seen many sound hole designs on here and was wondering what you use for reinforcement under and around those intricate designs.