Square rig

Square rig is a generic type of sail and rigging arrangement in which a sailing vessel's primary driving sails are carried on horizontal spars that are perpendicular (or square) to the median plane of the keel and masts of the vessel. These spars are called yards and their tips, outside the lifts, are called the yardarms. A ship mainly rigged so is called a square-rigger.

In "Jackspeak" (Royal Navy slang), it also refers to the dress uniform of Junior Ratings.