The ratchet wheel is attached to the barrel’s arbor through a screw. It is located on top of the barrel and turns around the mainspring when the watch is wound. It also coils the mainspring during winding. It assures that the mainspring is properly functioning with the support of the click. The click keeps the ratchet wheel in its appropriate place so that the mainspring will not unwind in the opposite way. When you hear the watch click, it is because of the ratchet wheel’s tooth that is tapped during winding.