The drawbridge was an important feature in the defence of a castle. In its most simple form it was a platform of timber turning upon two gudgeons or trunnions at the inner end; when up, it concealed the portal, and when down, dropped upon a pier in the ditch or upon the counterscarp. Its span varied from 8 to 12 feet. The contrivances for working it were various. Sometimes chains attached to its outer end passed through holes above the portal, and were worked within by hand or by a counterpoise. Occasionally there was a frame above the bridge, also on trunnions. In the larger castles the arrangements were very elaborate. Sometimes the bridge was the only connexion between the gateway and the opposite pier; at others the parapets or face walls rested on a fixed arch, and the bridge dropped between them. A fine example of this kind of bridge is seen at the Constable’s Gate, Dover Castle. At Goderich the details are tolerably perfect. The ditch was crossed by a stone bridge, apparently of two arches, but only the outer one is permanent. The roadway of the inner one was a drawbridge. At Caerphilly, in the ditch in front of the main gate, is a large stone pier from which a bridge fell each way. Probably it carried a tower of timber. In Henry III.’s accounts is mention of a _brétasche_ on the bridge of the great tower at Winchester, and of another, covered with lead, upon the new bridge. The portcullis, the “altera securitas” of the badge of the House of Somerset, always present in the castles of Henry and Edward, was an important part of the defence. It was a strong grating, in the smaller gateways of iron, in the larger of oak, strengthened and shod with iron spikes, and suspended in grooves by two cords or chains, which passed over two sheaves, or sometimes through a single central block, and either were attached to counterpoises or worked, as at the Tower and York gates, by a winch. The grooves are generally half-round, with slightly prolonged sides, 4 to 6 inches broad by from 4 to 7 inches deep. Above, in the vault, is a chase through which the grate is worked. Sometimes the portcullis chamber is a small cell in the wall, as at Rochester keep and Coucy, but in large gateways where there are two or three grates, they are worked in the chamber above. At Linlithgow and Thornton Abbey, where the grate is single, it is carried up within the wall and worked in the second story. Sometimes the grate had no lateral grooves, and must have either hung loose or been steadied by its spikes resting on the ground below. This is seen at St. Briavels and at the upper gate of Chepstow, though never with an outer portcullis. Sometimes grooves are cut for a spare grate, but do not appear to have been armed.