Lift locks on the C&O Canal have a generally uniform construction, typically stone walls and wooden gates which form a “V” that points uphill. Some locks have wooden bottoms instead of stone. Wikipedia presents the following view of a ” empty” canal lock below. A lock chamber is separated from the rest of the canal by an upper pair and a lower pair of mitre gates. The gates in each pair close against each other at an 18° angle to approximate an arch against the water pressure on the “upstream” side of the gates when the water level on the “downstream” side is lower.
The C&O Canal is 6 feet deep and has 74 lift locks. Originally 12 feet wide, erosion and time have narrowed the canal to as little as 7 feet wide today.
Here are a few photos from the canal:
You’ll notice a catwalk on the lock gate that allows a person to cross the canal without a bridge. The four vertical rods in the lock gate control doors (or paddles) in the gates which allow upstream water to flow into the lock to raise a canal boat. The beauty of this totally passive system to fill and empty the locks is very clever in an age before electric pumps.
Natural land features were used when possible to contain the canal, as the stone rock face on the right demonstrates.
Recesses were built into the sides of the lock walls so that the lock gates would be cut of the way of the canal boats as they passed through.
While not actually a lock, the last structure on the C&O Canal is in Cumberland MD, where the canal gets water from the adjacent Potomac River.