Yard & Yardarm
A Yard is a horizontal (or near-horizontal) spar set across a mast from which a square sail is hung on traditional square-rigged sailing ships. The Yardarm is the outer end of a yard — the tapered tip beyond the sail.
On square-rigged vessels the yards are hoisted and braced (angled) to set the sails to the wind, and the yardarms were used for signalling (hoisting flags), and historically for grim purposes. The phrase “the sun is over the yardarm” (traditionally the time for a first drink) derives from the sun rising above the yardarm in the forenoon. Yards and yardarms belong to the vocabulary of the traditional square rig, alongside masts, spars and rigging, and survive in sail-training and heritage vessels and in nautical language. They are part of the enduring terminology of a ship's rig.
The yard and yardarm are core to the square rig that drove ships for centuries — the spar that carried the sail and the arm that carried signal flags (and gave us "the sun is over the yardarm"). They are enduring pieces of nautical vocabulary that anchor an understanding of traditional rigging.
What is the difference between a yard and a yardarm?
The yard is the whole horizontal spar across the mast carrying a square sail; the yardarm is the outer end of that spar.
What does "the sun is over the yardarm" mean?
A traditional saying marking the time of day (late forenoon) when the sun has risen above the yardarm — proverbially, time for a drink.