HEADGATE
a gate for controlling the entry of water into a sluice, channel, etc.; specifically a gate or pair of gates at the upstream end of a canal lock.
a gate at the end of a cage, pen, or chute, used as an aid to handling livestock, which allows the head to pass through but restrains the shoulders.
a gate at the end of a cage, pen, or chute, used as an aid to handling livestock, which allows the head to pass through but restrains the shoulders.