Topmast staysail
A topmast staysail is a sharp, triangular sail  which is hoisted above the gaff sails.  It is hold in place with a halyard, two necklines, two tacks  and one or two loaders.  It is fixed on one side to a spar or antenna and on the other to the mast. It is hoisted when there is a slightly favorable weather, to increase the heeling of the boat and gain some speed. In some boats the topmast staysail has an irregular trapezoidal form; then the bottom overlaps slightly with the gaff sail.