In some examples, an apparatus includes a working surface including at least one material removal member. The material removal member is configured to remove at least some of a first portion of a first material. A protrusion extends outwardly from the working surface. The protrusion extends beyond the at least one material removal member by a first distance. The protrusion is configured to inhibit the at least one material removal member from removing at least a second portion of the first material. The second portion has a thickness substantially equal to the first distance.
