It is particularly important to set the cradle arms correctly before use, especially when a boat is to be hauled for the first time. The boat should be positioned centrally between the cradle arms.
Fore and aft position in the cradle is also needs to be correct.
Mark the waterline beforehand on the cradle arms so that when the cradle is that depth into the water it should allow for approximately 100 to 150 mm below the boat keel, as in the diagram.
White plastic wrapped around the arms with black tape marking the waterline shows up well at a distance.
Some narrow fin keeled boats may require webbing strops under the forward part of the hull to prevent the boat tipping forward in the cradle as the haul out proceeds.