What is the main function of a ratchet mechanism?

The main function of a ratchet mechanism is to permit movement in one direction only. This functionality is essential in applications where it is important to allow motion in a single direction while preventing reverse motion. Ratchets typically consist of a wheel or disc with a series of angled teeth, alongside a pawl that interacts with these teeth. When the mechanism is turned or moved in the designated direction, the pawl engages with the teeth and allows motion. When an attempt is made to move it in the opposite direction, the pawl secures itself against the teeth, effectively locking the mechanism and preventing backward movement.

In contrast, the other options describe mechanisms that either allow bidirectional motion, convert motion types, or improve mechanical advantage, which are not relevant to the primary function of a ratchet.