The previous owner of a speaker cab I just purchased had drilled some 5/16" holes around each of the speaker openings for some reason. The holes go all the way through. I know that I could just fill them up with caulk or wood putty but I want to know the real way that a furniture/cabinet maker or woodworker/craftsman type would fix this. I'm thinking I'll need to clean out the holes by drilling them out possibly to a larger size. Then shaping some wooden dowels and gluing. Am I on the right track? If so, will any old dowel do? What about the glue?