When you’re working with high torque, these wrenches keep the nut from turning as you tighten a bolt. You'll need a head and a handle to form a complete wrench. The head goes around the nut you want to hold stationary and the handle braces against an adjacent nut, absorbing the torque. They're often used when sealing large pipe flanges with a hydraulic torque wrench. Safer than striking wrenches, they stay securely on the nut until you release them.