A tension wrench is a simple tool used in the art of lock picking. It applies rotational pressure to the lock cylinder, allowing the locksmith to manipulate the pins inside the lock. By turning the tension wrench, the locksmith can create a slight tension that helps hold the pins in place while they are being picked. Typically made of metal or strong plastic, tension wrenches come in various sizes and shapes to fit different types of locks. They are often used alongside other tools, such as a lock pick, to successfully open a lock without a key.