Canal locks are structures used to raise and lower boats between stretches of water at different elevations. They work by filling or emptying a chamber with water, allowing vessels to move up or down a slope. When a boat enters the lock, gates close behind it, and water is either added or removed to change the water level. These locks are essential for navigating canals and rivers, making it possible for boats to travel across varied terrain. They help maintain water levels and ensure safe passage, contributing to the efficiency of maritime transport and trade.