When I was a kid my family had a lock that worked much like the one in the link. It had a metal strap that was bent on the end so it could be inserted into the door latch while closing the door. Then a metal pin was inserted into a hole in the strap and it had plastic ends that slipped on the pin to keep it from wiggling off.

While horsing around with my brother I grabbed the lock and used it to lock the door to my bedroom (the bedroom doors didn't have locks). One good shoulder to the door and the lock gave way and the door swung open. The bent end on the strap simply bent out straight, allowing the door to open.

Hopefully the strap on the lock in the link is MUCH stronger than the one we had.