Provide additional security for your family and home with the Atlas Double Cylinder Deadbolt Door Lock. Double cylinder deadbolts have a keyed cylinder on both sides. They require a key to lock or unlock the door from the inside and the outside. Choose a double cylinder deadbolt if you have a responsible key holder around at all times in case of emergency. Deadbolts are made to withstand amature attempted break-ins. By having a deadbolt on your door you are helping deter thieves from approaching your property. These deadbolts require a key lock or unlock the door from both sides.