In its strict maritime meaning a temporary deck laid in any part of a ship, the beams across which it is laid being known as skid beams. But the term was often used to describe the quarterdeck or forecastle deck of a deep-waisted ship, possibly because in the days of sail spare spars could be lashed to these decks as replacements for those damaged in use, rather than in the ship's waist. In the US Navy the term applied to the weather deck of its frigates, where the flimsy gangways formerly used to connect the forecastle and quarterdeck had been so expanded and strengthened as to create a continuous deck capable of supporting guns. The ships themselves were sometimes referred to as ‘spar deck frigates’. In modern usage, the term is sometimes employed to describe the upper deck of a flush-decked ship.