Spreader Devil DQ
A cringle in the leech of the sail that is close to the boom is a flattening reef cringle. Before loose footed sails became the norm again, flattening reefs were needed to take some of the draft out of the sail when beating in a breeze. With a conventional shelf foot mainsail (or bolt rope mainsail) pulling aft on the outhaul only flattened a narrow band of the sail near the boom and did not pull cloth out of the lower portion of the sail as would be ideal. The geometry of a flattening reef actually pulls cloth diagonally and so flattens further up into body of the sail. While this was primarily a circa 1973-1983 hot racing set up, if the sail was cut for a flattening reef then using the flattening reef as the wind builds on a beat can be very helpful.