now it says unknown comman "+weapon10"

ok, new problem. i tried typing /bind g weapon10 and it says unknown command weapon 10. help!

ty. u all rock!

I hope i posted in the right place... in one of the online arenas, there is a weapon, a grappling hook. A couple of _bleep_ found out how to use it and their using it to their advantage. I was wondering if anyone could tell me how to use it.