A sailboat's tack plate is a metal fitting used to secure the tack—the forward lower corner—of a sail to the deck, mast, or bowsprit. It provides a strong, fixed anchor point for the sail's luff, crucial for holding the sail's forward corner in place while under wind pressure.

Location: For the mainsail, the tack is secured to a fitting where the boom and mast meet. For headsails (jib), the tack plate is usually on the bow, bowsprit, or deck, often attached to a furling drum.

Function: It holds the tension of the sail's luff and foot, keeping the sail connected to the boat.

Structure: They are typically made of stainless steel or aluminum, featuring holes to attach shackles or downhaul lines (such as a Cunningham).

Related Components: Often used in conjunction with a downhaul or cunningham to adjust tension.

These plates are distinct from the tack (the maneuver of changing directions) or the tack (the corner of the sail itself).