A guide for a mooring line, or steel towing wire which enables the line to pass through a ship bulwark or other barrier. See also Fairlead, and Arrangement of chocks and bitts for transit of Panama Canal.
- Double chock – A large chock capable of withstanding the stress caused by a load of two towing wires. According to requirements of the Panama Canal the double chock is a closed chock that has a throat opening of not less than 900 cm2 area, and is capable of withstanding the stress caused by a load of 64,000kg from the towing wires in any direction.
- Single chock – Chock designed for a single towing wire. According to the requirements of the Panama Canal the single chock is a closed chock that has a throat opening of not less than 650 cm2 area, and is capable of withstanding the stress caused by a load of 45,360kg from a towing wire in any direction.
