What is a hook block and what does it do?

• A. A counterweight assembly
• B. A spare hook kept as a backup
• C. A safety lock that prevents hoisting
• D. The assembly that carries the hook and attaches to the hoist rope, transmitting lifting force to the load

Answer: (D)

The hook block is the lower part of the crane’s hoisting system that carries the hook and the rope’s pulleys. Its job is to attach to the hoist rope and move with the load, turning the rope’s tension into the lifting force that is applied to the load through the hook. Inside it are one or more sheaves (pulleys) that guide the rope, which can also provide mechanical advantage depending on the reeving. The hook often has a safety latch to keep the load secure. It’s not a counterweight, not a spare hook, and not a safety lock; its purpose is to transmit the lifting force from the rope to the load via the hook.