On Thu, 13 May 2004 10:18:46 -0400, "Gary Warner"
wrote:
What is a Jackline?
It is a line running from the tack of the sail up the luff approximately the
distance of four slides. This line is secured to the sail at the top and
tied to the fitting at the tack. The jackline is threaded through pairs of
grommets that are on the luff of the sail. Hardware to attach the sail at
the intervals is threaded on the line between each thimble pair.

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What you are describing are "lazy jacks" which are used to keep a
mainsail under control while raising and lowering.

Jack lines are different. They are run fore and aft along each side
of the boat, allowing you to be clipped on with your safety harness at
all times but still be able to maneuver on deck.