A tower at the entrance to a castle or fortified town
An opening in the wall of a fortress through which the guns are levelled; a narrow loophole through which arrows and other missiles may be shot.
A fortress at the end of a bridge.
A temporary wooden tower built for defensive purposes.
A building for the porter(s) near the gate of a castle, college, etc., (historical) formerly used as a place of punishment for the staff.
An equivalent room near the gate of a college, chiefly used as a mailroom.