Pencil sharpener of 6 cuts and takes practice to master without breaking the lead. Specialized sharpeners are available that operate on non-standard sizes of pencil, such as crayons used in primary schools. Sharpeners that have two openings, one for normal pencils and one for larger crayons, are fairly common. An artist's or draftsman's pencil sharpener leaves the graphite untouched and sharpens only the wood (some models can switch from standard to wood-only by an adjustment). The graphite lead is then honed to a sharp point with a lead pointer, which sharpens only the lead without wood. Lead pointers are also used with
Mechanical pencil collar that, when depressed as the lead is worn away, extends out again when pressure is released. An advanced ratchet type has a mechanism that rotates the pencil lead 9° counter-clockwise every time the lead is pressed on to the paper (which counts as one stroke), to distribute wear evenly. This "auto-rotation" mechanism keeps the lead 50% narrower than in the common propelling mechanical pencils, resulting in uniform thickness of the lines written onto the paper. The design was first developed by Mitsubishi Pencil Company, and named "Kuru Toga" under the Uni brand. This type of pencil is most suited