Geograph - photograph every grid square

Next to the top gate of the lock is the winding gear for the ground paddle, which allows boaters to let water from the higher level through an underground sluice into the lock while the water pressure keeps the lock gate shut. This fills the lock and will therefore lift any boat inside the lock to the upper level. The winding gear is operated by a windlass (handle) which boaters carry with them and which fits either of the tapered spindles protruding sideways from the mechanism. The bracket at the front (the pawl) ensures that the windlass isn't pushed back by the water if the operator accidentally lets go of it. Once the level inside of the lock is close to the level outside the lock gate, the gate can be opened by pushing the balance beam (seen here behind the winding gear). Link