Some bivalves are able to bore into wood or even solid rock using a variety of mechanisms.

Lithophaga (‘rock-eater’) secretes a weak acid from its mantle, then mechanically erodes the weakened rock by rotating its shell. The photograph on the right shows a thick bivalve shell that has been bored into by Lithophaga. The white arrow points to an individual Lithophaga shell inside its burrow.

Ship worms (Family Teredinidae) are not worms at all but are highly adapted bivalves that bore into wood using their shell as a file. These were a serious pest to merchant and naval shipping when ships were constructed of wood. The image to the left shows a piece of wood that has been bored into by ship worm.

Piddocks use mechanical abrasion alone to bore into soft rocks. the image to the right shows a sedimentary rock and the shells of the piddocks that have bored into it.