It is a Weslock with a cylindrical button on the inside next to the doorknob. A previous owner drilled a quarter inch hole on the outside opposite the button and I can see the butt end of the button through the hole. From the inside I can turn the button a half turn and it can easily be wiggled a lot, so is quite loose. I cannot get it to lock when I try, but sometimes when exiting and closing the door behind me I later find I cannot turn the doorknob and am effectively locked out. I think the think is broken because I cannot get it to lock, but that is OK as long as I can permanently keep it from "mysteriously" locking. Obviously, I can just put a new one in, but if there is an easy way to disable the locking mechanism that would be preferred.