a firearm support cushion or insert for a lock assembly . the inserts are formed to accept and restrain the fore - stock and / or receiver of a variety of specific firearms , for example , pump and auto - loading shotguns and rifles . the inserts include surfaces and / or recesses that conform to the contours of predetermined portions of a firearm . fastener mechanisms facilitate a detachable mounting of the inserts to the lock assembly and whereby a user can periodically adapt the lock to accept different types of firearms .