crowfoot wrench crow's-foot wrench: crow's foot: A type of wrench designed to use the same drive sizes as socket wrenches, but non-cylindrical in shape. The ends are the same as those found on the open-end, box-end, or the flare-nut wrenches. These wrenches are used when torque must be measured, or when the application precludes the use of a regular socket or wrench.