Locks

The sequence to descend a lock goes thus: If the lock is empty, you must first shut the bottom gates and fill the lock by opening the top paddles (and closing the bottom ones). When the lock is full you can open the top gates and the boat can enter the lock.

With the top paddles now down and the top gates closed, you now open the bottom paddles and the water level inside the lock equalises with that of the lower level in the pound below the lock. There is always almost a cill underneath the top gates which extends out into the lock for a couple of feet. Care must be taken to avoid getting caught up on the cill, else disaster can overtake the unwary. The furthest extent of the cill is normally marked in white on the side of the lock and can be up to 6 feet or more from the lock gates.

Lastly, once the water inside the lock is the same as that below the lock, you can open the bottom gates and the boat sails off into the distance (normally, but not always, after letting the bottom paddles down and closing the bottom gates again).

These are usually found at the top of locks and are a simple rack and pinion system. The water enters via the base of the lock chamber and causes the boat to surge backwards initially and then surge forwards as the level rises.

These come in various designs, some rack and pinion via a gearing wheel, some hydraulic (found a lot on the K&A) and can sluice the water in above or below the water level. These need treating with respect, as opening fully, too soon, can cause the flooding of a boat which is well forward in the lock; with full length boats this is a major detail as they must position themselves to the front of the lock, because of their length. ( Dawn has her own name for some of the more difficult paddles.)