Cut a sheet of acetate into a 17.5-cm/7-in square.
Spread the tempered chocolate on the acetate.
When the chocolate has semi-crystallized, cut out 12 triangles measuring 1.25cm/.5in wide by 15cm/6in long.
Wrap parchment paper around a 10-cm/4-in diameter PVC tube to prevent the chocolate from sticking, and then wrap the acetate sheet around the tube. Wrap the acetate with parchment as well to keep it in place, and tape it closed.
Let the chocolate set on the tube. Reserve in a cool, dry place.