A spreader patch is a fabric reinforcement at a point on a sail where it is likely to rub with the spreader on a mast.
Use and construction
Spreader patches may be placed on a jib,[1] when it overlaps with the mast, or on the mainsail,[2] where it may interfere when furled, or when the sail is backwinded against the mast.[3] Patches may be made of tape, sticky-backed Dacron, or other material that is compatible with the type of sailcloth being reinforced.[4] When applying such patches, it's important to affix it starting from the inner part of the sail, towards the edge of the sail (leech).[5]
References