This was a type of movable bridge which allowed access to a castle or related fortification, normally over a Moat or similar defensive ditch. Generally part of a Guard or Gate House structure, they were “mechanical” innovations. Normally ropes or chains attached to a windlass in a Gatehouse chamber would be “activated” by manpower. Counterweights would be employed to augment the massive amounts of strength that would be needed (to open and close the Drawbridge). Made from wood (often reinforced) or in some cases iron – they served as a primary defense against attack.