Many stringed instruments traditionally have binding around the edges of the soundboard. The binding protects the exposed end grain of the soundboard from damage. Dulcimer soundboards usually are not bound. I assume this was because many early dulcimer makers were not trained luthiers and they may not have had the tools, technique or inclination to add binding to their instruments.
I like the look of binding on a dulcimer. The binding accents the look of the dulcimer not unlike the way a frame displays a picture. The binding also prevents many of the dents and gouges the edges of most dulcimers collect over time.
A rabbett is routed around the edges of the dulcimer.
The binding is held in place with masking tape until the glue dries.
When the tape is removed the binding is scraped flush with the top and sides. Here’s the bound soundboard.
Of the many tools I use the coffee cup in the photograph is among the most important. That must be why it was on the bench when I took the picture….