Rough Limpets (Lottia scabra) are known for having home scars — a site that the limpet returns to consistently when not foraging.
Home scars can be multi-dimensional, with the upper level of the home scar fitting the shell margin, and the lower level fitting the shape of the foot. The scars are often eroded into rock, although in the case shown above, the form-fitting scar is worn into a layer of pink crustose coralline algae.
Can you see how this intertidal limpet fits into the scar (at the left) by matching the shape of the shell to the outline of the home scar?
Scientists studying the benefits of home scars have shown that the scars can prevent desiccation, reduce predation (with many predators, but not all), and increase survival after burial by sand.
P.S. If you're curious about orientation, the head of the limpet is at the narrow end of the shell.