| This question gets asked about once a week. If it's a finished maple fingerboard, alcohol (rubbing alcohol or methyl hydrate, which is a bit purer), naptha, paint thinner (mineral spirits-Varsol is one brand name) or even water with a little bit of dish soap works. I like the methyl hydrate myself. Don't get alcohol on real nitro finishes (very few new basses have nitro finishes) or on nitro pickguards as it can damage them. It won't hurt a poly, tung oil, or varnish finish. | 
