not all of them are for bolt on guitars, the fender type necks go w/o a doubt but those gibson style necks can go with the lespauls also. u just gotta undo the glue on ur lp, put the new neck on it and glue it back...alot of work though this one.
will never recommend taking out a set neck and glue a new one in. too much hassle and if it doesn't fit, have fun putting the neck back! the work is just not worth it. u can unscrew and screw in a bolt on neck for a few minutes but removing a set neck and putting a new one in might take days! if it turned out bad then sorry la.