Cyanoacrylate. Aka, super glue.

I prefer to rub on a CA finish and buff as appropriate instead of spraying on polyurethane. PUR is less brittle than CA, but the spray on application is often less even, and isn't absorbed into the wood as well as a properly rubbed CA. Both work, I just prefer CA - which to be clear - I drastically prefer a rubbed oil finish over a polymer coat any day, but I know many of these laminate wood stocks like the keystone and Boyd's come polymer sealed.