Sea-gate

A drawbridge or draw-bridge is a type of movable bridge typically associated with the entrance of a castle and a number of towers, surrounded by a moat. In some forms of English, including American English, the word drawbridge commonly refers to all types of movable bridges, such as bascule bridges, vertical-lift bridges and swing bridges, but this article concerns the narrower, more historical definition of the term.

Medieval castles were usually defended by a ditch or moat, crossed by wooden bridge. In early castles the bridge might be designed to be destroyed or removed in the event of an attack, but drawbridges became very common. A typical arrangement would have the drawbridge immediately outside a gatehouse, consisting of a wooden deck with one edge hinged or pivoting at the gatehouse threshold, so that in the raised position the bridge would be flush against the gate, forming an additional barrier to entry. It would be backed by one or more portcullises and gates. Access to the bridge could be resisted with missiles from machicolations above or arrow slits in flanking towers.

The bridge would be raised or lowered using ropes or chains attached to a windlass in a chamber in the gatehouse above the gate-passage. Only a very light bridge could be raised in this way without any form of counterweight, so some form of bascule arrangement is normally found. The bridge may extend into the gate-passage beyond the pivot point, either over a pit into which the internal portion can swing (providing a further obstacle to attack), or in the form of counterweighted beams that drop into slots in the floor.

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