On sailing ships, the jury rig is a replacement mast and yards improvised in case of loss of the original mast. The term "jury" is believed (Skeat) to have its source in a Latin and Old French root meaning "aid" or "succour".

While ships typically carried a number of spare spars such as topmasts, the lower masts, at up to one meter in diameter, were too large to carry spares. So a jury mast was a spare topmast, or perhaps the main boom of a brig. Another possibility, mentioned in W. Brady's The Kedge Anchor (1852), was to replace the foremast with the mizzenmast. Contemporary drawings and paintings show a wide variety of jury rigs, attesting to the creativity of sailors faced with the need to save their ships.

Ships always carried a variety of spare sails, so rigging the jury mast once erected was mostly a matter of selecting appropriately sized spares.

Although ships were observed to perform reasonably well under jury rig, the rig was quite a bit weaker than the original, and the ship's first priority was normally to steer for the nearest friendly port and acquire replacement masts.

The term "jury-rigged" has since passed into general usage, denoting some improvised substitute was employed temporarily or in an emergency.

See also: sailing ship accidents

Reference

• John Harland, Seamanship in the Age of Sail (Naval Institute Press, 1984)