The small and discreet–but effective–Defender works much like a door blocker. When it’s in the locked position, it rests in a slot and can withstand up to 800 lbs. of force. To unlock it, you slide it up and swing it out.
There are no keyholes that can be picked, and unlike a swing latch or chain, it doesn’t allow your door to open even a crack, so it can’t be tampered with. At under $10, it’s also easy on your wallet.
It fits most exterior doors, but it’s probably not a great choice if your apartment door fits snugly in its frame, as you might have to chisel out a chunk of the frame to get the security lock to fit. Our research showed that some of these locks come with rough, sharp edges that might require some filing down.
Users also say that the lock loses functionality if you’re using it to lock the door several times a day for more than a year.2