TrySail

A trysail is a small triangular or gaff rigged sail hoisted in place of a larger mainsail when winds are very high. The trysail provides enough thrust to maintain control of the ship, e.g. to avoid ship damage, and to keep the bow to the wind. It is hoisted abaft the mainmast or, on a brig, abaft the foremast. A trysail is analogous to a storm jib.