How do the serrations on a Yale key raise pins inside a cylinder lock?

In a Yale cylinder lock, the serrations on the edge of the key function by lifting internal pin tumblers to specific, predetermined heights.12

When the correct key is inserted into the lock, these serrations push the pins upward so that they align perfectly with the shear line—the boundary between the inner cylinder and the outer housing. Once all the pins are raised to this exact height, the obstruction is cleared, allowing the cylinder to rotate and withdraw the bolt. If the serrations do not match the required pin heights, the pins remain in a position that blocks the cylinder from turning, thereby maintaining the lock's security.12