Foot
The lower edge of a sail between tack and clew.
How to sign
Use Dominant flat-B or 1-hand, palm down. The base or passive hand is Non-dominant flat-B: sail plane. Set the sail triangle. Put the active hand at the tack/low forward corner. Trace the bottom edge in one horizontal or slightly rising path to the clew. Hold at the low aft clew endpoint. Establish a sail triangle. With a flat-B or 1-hand, trace the bottom edge from tack to clew in one horizontal or slightly rising movement.