Why do Canals Have Locks?

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Canals are water ways built by man to carry water traffic. When they are built across high ground in a hilly area, they have to change level at a lock. A lock is like a step. It raises or lowers boats on the canal from one level to another. A boat travelling upstream enters the lock through a pair of lock gates, which close behind it. Sluices at the other end of the lock are opened to let water in, and gradually the water level in the lock rises, when water is in the same level as that beyond the lock, the farther gates are opened to allow the boat to pass through.

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