Without as much as a wave shepherd moons Prometheus and Atlas pass by each other, each on their own paths around the rings.
Prometheus, casting a long shadow, pulls at the F ring’s bands of material while smaller Atlas guards the edges of the A ring. The larger is 93 miles across at its widest point, the other is 23 miles wide. Both moons are irregularly-shaped, Prometheus extremely so.
The vertical banding visible in this modified raw image is a result of Cassini’s imager, not a feature of the rings. See the original image here.