A bridge, hinged at one end, that can be lifted via a system of chains, counterweights and winches. Used in conjunction with a moat, the drawbridge in a raised position would restrict access to the castle walls and keep. Besieging forces would need to use boats, drain the moat or wait until defenders surrendered due to lack of food or water. 

Pictured is the is the drawbridge at Arundel castle.

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