To prevent the rack and the paddle from dropping back down once the windlass key is removed, there is a pawl or metal hook that works against the teeth of a gear (the ratchet) that’s on the spindle. To crank the paddles back down, the pawl must be disengaged by pulling it away from the gear. In order to raise the pawl, you’ll have to slightly turn the windlass key in the opposite direction that the teeth on the ratchet are pointing.
Leonardo da Vinci invented the mitered lock gate. Most gates are angled 18° to approximate an arch. Mitered gates point uphill and the pressure of the water keeps them shut.
The balance beams attached to the gates are very long for two reasons—to make a longer lever for closing the very heavy gates and to counter-balance the weight of the gate itself. Lock gates can hardly be said to be hinged. They fit into a rounded groove in the pound walls, held in place by relatively thin metal straps and the pressure of the water. Essentially the oak gates float in the water.
The gates of the lock are opened by pushing the attached balance beams. To help a boater push against the beam, there are usually raised bricks set in the ground to provide footing while pushing or pulling the beams.
The uphill gates open outward, into the canal. The downhill gates open inward, into the pound.
There is a cill—a masonry or concrete shelf—just inside the uphill lock or gate. The gate (or gates) shuts against the cill. When the lock chamber is filled, a boat entering the lock rides over the cill when going downhill. There is a warning on the walls of the lock chamber to indicate the edge of the cill.
There are usually ladders built into the side of the lock chamber. They’re narrow and slippery and primarily there for the convenience of a boat crewed by one person, to let that person go up to open or close paddles and gates or go down to drive the boat out of the lock. A person who falls into a lock can also climb the ladder to safety.
There are either bollards or mooring rings on either side of the lock chamber, again chiefly for the convenience of one-person boats, to keep the boat from drifting too close to the cill by wrapping the center line around one of the bollards.
At the downhill end, water is let out of the lock either through sluices in the banks or paddles in the gates. If there are gate paddles, the spindle or shaft that turns the pinion (which raises the rack and the attached paddle) runs along the balance beam you push to open and close the gate.
Usually there’s a walkway that runs along the top of the outside face of the downhill gate. You cross the lock on that narrow platform, keeping a hand on the railing that is attached to the beam. There’s usually a similar platform on the uphill gate. It can be a little unnerving crossing the lock the first time and you’ll be thankful for the non-slip surface on the platform. Occasionally there’s a more substantial bridge on the downhill side.