When a lever is pushed downward or a knob is turned, it rotates a spindle passing through the door. The spindle operates the latch mechanism, pulling the latch bolt away from the strike plate so the door can open.

A door handle works in a simple way, but the way it feels in daily use depends on much more than one moving part. The hand pulls or presses, the force transfers into the fixing points and lock structure, and the door responds. When that process feels smooth, people rarely think about it. When it feels loose, awkward, or badly matched to the door, it becomes obvious very quickly.