Indicator contact points can vary by numerous different shapes, and each one has a specific use for which it is best suited. The ball point shape is the most common and can be used for workpieces with deep indentations. The shell type point is best used with flat surfaces due to its large radius. Also having a large radius, the spherical point is suitable for when workpieces need to be mobile and move from side to side. A conical point may be used for positioning the measurement point, but be careful because this type of point should not be used on soft materials. An indicator contact point with a flat point is usually best for convex surfaces, while a knife edge point is usually best for getting a measurement of the diameter in a narrow groove. A needle point shape best suits the measurement of the bottom of a hole or groove. The blade point shape is best for convex surfaces with shallow grooves. Last but not least, a roller point contact point may be used when the workpiece needs to be moved for the measurement to take place.