Often during docking of large ships the dock lines cannot be made tight enough using manpower alone. Therefore one end of the mooring line is sent ashore and affixed (placed on a bollard) and tension is applied using a powered winch. The line must then be transferred from the winch to the bitts onboard the vessel without losing that tension. For this purpose it is “stopped” – a shorter line takes the strain while the mooring line can be then removed from the winch and secured onto the bitts or other fixture designed for this purpose. The stopper is then slowly released and the transfer is complete.
An older application for the stopper hitch is when using a winch or multiple crew to raise sail. The tension must be moved from the multiple deckhands holding the line to a cleat or similar fixture. A stopper is temporarily applied, the line is moved and secured, and the stopper is removed.
Essentially a rolling hitch with the bitter end either married (held) against the standing part under strain if the evolution is quick, or it is seized if the stopper will be in place for any length of time, which is unusual, although some blocks have been placed in the rigging using selvagees stoppered to shrouds then seized.
Using two lines instead of one, they may be criss-crossed about the line tension is being transferred from. The advantage of using two lines is that as no passes or knots are made, they will not jam or bind on the line under tension.
A similar method may be employed on wire rope using chain. Chain is the only suitable material for use as a stopper for wire rope.