A cringle is a reinforced eye or hole, typically rimmed with stranded rope or a metal grommet, located along the edges or corners of a sail. It is used to pass lines through for strengthening, sail handling, or reducing sail area, often in conjunction with reefing lines.

Key Aspects of a Cringle
Purpose: Primarily used for strengthening the sail at attachment points, allowing for reefing lines (cringle reefing) or as anchor points for Cunningham controls.

Construction: Traditionally made by working a rope loop into the boltrope, but modern cringles frequently feature reinforced metal grommets to reduce wear.

Common Locations:

Reefing Cringle: Located along the luff and leech to hook onto the boom (tack/clew reef cringle) when reducing sail in high winds.

Corner Cringle: Located at the tack, clew, or head for attaching the sail to the rig.

Use Cases: Essential for securing the tack and clew to the boom during reefing, ensuring the sail maintains its shape.

Cringles allow for adjusting the tension and shape of the sail for better performance in various wind conditions.