A wrench or spanner is a tool used to provide grip and mechanical advantage in applying torque to turn rotary fasteners such as nuts bolts or to prevent rotation. Wrenches are made in SAE, metric and adjustable configurations to fit a wide variety of fastener sizes and may employ features such as high voltage insulation or angled ends for special conditions. Common tool types are box end, open end, ratcheting, combination, torque and lineman's wrenches.