Danger
As mentioned before, locks are relatively simple and you’ll soon become an expert at turning them, but with skill often comes complacency. Please be sober when turning a lock, especially the driver. Carelessness can cause damage to the boat, damage to the lock, usually damage to both and very, very infrequently loss of life.
Lock gates are mostly built of oak. The paddles used to be made of elm, but Dutch elm disease has made elm scarce and so now paddles are also made of oak. Various pine wood is used for railings and embankments.
Beware the cill
The biggest danger is being caught on the cill. The cill is the masonry or concrete structure against which the uphill gate closes. There’s a similar ledge against which the downhill gate closes, but it’s less noticeable. Staircase locks, however, share cills. Some cills are stair-stepped, so you might think you’ve cleared it but you haven’t.
You’re at most risk going downhill, when the stern of the boat is caught up on the cill. It’s nearly impossible to get the front of the boat caught on the cill going uphill, but it is possible to swamp the front of the boat when opening the uphill paddles too quickly. It’s a good idea to close the front doors of the boat when going uphill and to open uphill paddles gradually.
If there are both ground and gate paddles on the uphill side, open the ground paddles first until the boat is high enough that the inflow from the gate paddles won’t swamp the boat.
Rebound
The other danger is rebound, caused by the flow of water into the pound from the uphill sluice or gate paddles. Going uphill, you might have taken care to avoid the uphill gate, probably applying a little reverse thrust to keep the boat from actually hitting the gate. But as water comes into the pound, it hits the closed lower gate, rebounds and pushes the boat forward.
Falling in
Throw a life preserver to anyone who falls into the lock pound and if possible a line. Put the engine into neutral and try to keep the boat still. Close all paddles, however it may be necessary to either let water in if the pound is almost full to allow the person to swim to the edge of the pound and climb out. Or release water from the pound if the pound is almost empty and open the lower gate. Don’t jump in to save them; you’ll just end up with two people in the pound.
Going too fast
Going too fast through a lock is probably what causes the most cumulative damage to a lock. The gates last about 20 years before replacing. You’ll notice they’re protected with steel plates, but careless and drunken boaters have occasionally broken out the vertical slats or even dislodged gates.
Open both lock gates when entering or leaving a lock.
Don’t push open a partially closed gate with the boat’s hull—that could damage the edge of the gate and cause it to leak.