A ring about 3 mm in length is cut from a tube of Plexiglas (polymethylmethacrylate) of 2 cm outside diameter, and is glued to the centre of a microscope slide. It is partly filled with a cold-setting polyester resin, and the fragment of which a cross-section is to be made is placed vertically in a small cut made in the set resin. The remainder of the ring is filled with resin. After setting, the resin is ground down and polished to reveal the cross-section.