jackstay

1. A stay (rope, bar or batten), running along a ship's yard, to which is attached the head of a square sail.

2. A cable between two ships or from a ship to a fixed point which can be used to support a load during transfer of personnel or materiel along the cable.

3. A line (rope, webbing or cable), attached to a boat at the ends, to which a safety harness can be clipped to restrain falling in rough conditions and to prevent falling overboard.

4. A line fixed at both ends, which may be used to guide a load or a diver along the route of the line. Uses include guidance to and from the underwater work site, and as a means of controlling an underwater search.

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