How A Lock Works
How A Lock Works
Boat Going Downstream
Virtual Lock - Downstream

Boat Going Upstream
Virtual Lock - Upstream

Unanimated Version
Boat Going Downstream

Boat enters the lock; gate closes behind it.

Water is released downstream; water level lowers in the lock.

When the water level is low enough, the gate opens and the boat leaves the lock.
Boat Going Upstream

Boat enters the lock; gate closes behind it.

Water enters from upstream; water level rises in the lock.

When the water level is high enough, the gate opens and the boat leaves the lock.