The new lock at Combined, opened in 1974, is one of three automated locks on the Rideau Canal. Like all locks on the canal, it moves boats by raising and lowering water levels, but unlike manually operated locks, where Parks Canada staff crank winches by brute strength to open and close gates and sluice valves, this lock uses electrically operated hydraulic valves controlled by staff pushing buttons. In an upbound lockage, a boat enters with water at the downstream level, the lower gates are closed, upstream sluice valves are opened to fill the chamber, the water rises until it equals the upstream level, the gates are opened, the sluice valves are closed, and the boat leaves. In a downbound lockage, a boat enters with water at the upstream level, the gates are closed, downstream sluice valves are opened to lower the water in the chamber, the water falls until it equals the downstream level, the gates are opened, the sluice valves are closed, and the boat leaves. The lock has a 26 foot 8 metre lift, the highest on the system, solid timber gates, electric powered hydraulic systems for the sluice valves and gates, floor openings designed to reduce turbulence as water enters the chamber, and a vent through which air escapes as water travels the tunnel below.