One of the many live snails I photographed last June when I was in Turkey was this juvenile of the species formerly known as Helix aspersa. After the photo session, I released it back to the wild, but its photos are now in my records with the code name HA1.
HA1 was one subject in an ongoing study looking at the relations between the dimensions of snails' feet and shells. One way of getting that information is to take pictures of snails from below while they are crawling on glass. The ruler provides the necessary scale.
When I took a closer look at the above picture a few months later, I noticed that the snail's jaw was also visible. Here is the relevant detail from the same picture.
Despite its name, the gastropod jaw is only remotely analogous to the vertebrate jaw. The jaw is attached transversely to the upper margin of the mouth. The snail uses its jaw to scrape off food particles, for example, algae, from surfaces or to rip off pieces of food, for example, leaves, and to push them into the mouth cavity.