Mollusks use a structure called a radula to scrape food off of rocks. The radula is a ribbon-like structure located in the mouth of most mollusks. It is covered in rows of tiny, tooth-like structures called radula teeth, which are used to scrape, shred, and tear food.

Here's how it works:

* The radula is moved back and forth, scraping against the surface of the food.

* The radula teeth are constantly being replaced as they wear down.

* The food is then transported to the mouth, where it is further broken down and digested.

Different mollusks have different radula shapes and sizes, depending on their diet. For example, herbivorous mollusks have radula teeth that are sharp and pointed, while carnivorous mollusks have radula teeth that are more hook-like.