The tension wrench, or torsion wrench, is generally used when picking a pin tumbler or wafer lock. It is used to apply torque to the plug of a lock to hold any picked pins in place. Once all pins are picked, the tension wrench is then used to turn the plug and open the lock. There are two basic types of tension: "bottom of the keyway" and "top of the keyway". The bottom of the keyway wrenches is typically shaped like a letter "L", although the vertical part of the letter is elongated in comparison to the horizontal part. Other tension tools, especially those for use with cars, resemble a pair of tweezers and allow the user to apply torque to both the top and the bottom of the lock. These are commonly used with double-sided wafer locks.