The copy sleeve is an accessory for the top milling machine, which is used to accurately guide the machine according to the template or ruler. It is a ring, usually metal, that is attached to the base of the milling machine. The milling tool itself, the cutter, passes through the centre of this ring. As you work, the outer edge of the collet then slides over the edge of the prepared template, ensuring that the cutter cuts a shape that is an exact copy of the template. An important concept here is the so-called "indentation" or offset. Because the collet is wider than the cutter, the resulting groove or cut is not made right at the edge of the template, but some distance from it. This offset has to be taken into account when the template itself is produced, so that the final product has the desired dimensions. These accessories are used, for example, for cutting out more complex shapes, decorative elements or for making precise joints and inserting other materials.