What is the meaning of Bitts?

A frame of two strong timbers fixed perpendicularly in the fore part of a ship, on which to fasten the cables as the ship rides at anchor, or in warping. Other bitts are used for belaying (belaying bitts), for sustaining the windlass (carrick bitts, winch bitts, or windlass bitts), to hold the pawls of the windlass (pawl bitts) etc.

Source: Webster’s Revised Unabridged Dictionary (1913), via OPTED