Above are samples of the ingenious Kiwi slides, one small, one medium. The six available sizes have breaking strengths from 506 pounds to 1430 pounds, generally far beyond what a sail would exert. The biggest strain on sail slides, slugs, or shackles occurs not in hard winds, but while slatting—a sail popping sharply back and forth in sloppy conditions.

Kiwi Slides

No matter how beautiful or well-made working sails are, their efficiency is greatly affected by the manner in which they are attached to a mast or forestay. There are lots of lousy sails in use—partly because they weren't very good to begin with or have been unmercifully stretched, soaked, and wrinkled—but even a lousy sail will function better than a good one if its attachment system is superior. As an engineer would say, sails are your primary source of propulsion, but they have to be set in place properly to work.…