Locks work by opening and closing gates and pumping water in and out of the closed gates to float the boat up and down, like a lift. Locks are used to let boats go up and down canals or rivers, because if the river has a weir in it, the boat can't go up or down it without a lock.
How to operate a lock: Going up river.
First, if the gate isn't open you need to open it. Get out of the boat and close the gates at the far end - you may need some help. Use a lock key to wind up the paddle in the pair of gates closest to the boat to let the water out; one will do but two is faster especially for a deep lock. When the water level in the lock is equal to the water level around the boat wind the paddle/s back down. Once that is done you can open the gates, bring the boat in and tie her up from both ends. Next,close the gates and use the lock key to wind up the paddles and let the water back in. The ropes will loosen as you go up so you might want to have someone at each end tightening the ropes. Once the water level in the lock in equal with the water level in front, wind the paddles back down, open the gates ahead and sail the boat out.
When going downstream it is pretty much the reverse operation except for these few differences:
-keep the boat clear of the sill mark.
-loosen off the ropes when going down so the boat doesn't hang from the side of the lock!