A tension wrench, also known as a tension tool, is a simple device used in the art of lock picking. It applies rotational force to the lock cylinder, allowing the locksmith to manipulate the pins inside the lock. This tool is essential for successfully opening pin tumbler locks without a key. Typically made of metal or strong plastic, tension wrenches come in various shapes and sizes to fit different locks. They are often used in conjunction with other lock picking tools, such as pick tools, to effectively unlock doors and safes. Proper technique and practice are crucial for successful use.