The roundel is similar in basic form to the flat chisel except that its cutting edge is curved rather than flat. It is a metal hand-held tool which is struck with a metal hammer or wooden mallet, consisting of a shaft, 15-25 cm long and 1-2 cm in diameter. The curve of the cutting edge varies considerably from a semicircle to a barely discernible curve. There is fine line between flat chisels with rounded corners and roundels. The roundel can be used for rough and smooth work and is well-suited to delicate areas of carving since it has no corners that might catch on anything. It is especially suited to carving hollows since its shape fits the curves. Occasionally it is also used for surface texture, especially on natural forms like trees or rocks. Like the flat and tooth chisel, the roundel is usually held at 35-60° to the surface of stone. It is often used on marble and very common on softer stones but almost never used on granite.