Shepherd moon

This can carve gaps in the ring system, such as the Encke Gap maintained by Saturn's moon Pan, or lead to the confining of narrow ringlets, such as Saturn's F ring.

To explain this, Goldreich and Tremaine suggested that two small satellites that were undetected at the time might be confining each ring.

[3] It is possible that these rings are composed of material that is being pulled off these two bodies by Jupiter's tidal forces, possibly facilitated by impacts of ring material on their surfaces.

[7] Uranus also has shepherd moons on its ε ring, Cordelia and Ophelia.

[13] A major gap in the circumstellar disk or large ring system of the free-floating brown dwarf or rogue planet J1407b at about 61 million km (0.4 AU) from its center is considered to be indirect evidence of the existence of an exomoon (or exoplanet) with mass up to 0.8 Earth masses.

Prometheus (right) and Pandora (left) both orbit near Saturn's F ring, but only Prometheus is thought to act as a shepherd.
Operation of a shepherd moon– particles are located in front or behind the Moon in its orbit, so these are either accelerated in the direction of the moon and thrown to the outside, or they are slowed on their path and pulled inwards.