Drawing parallel lines on a cylinder
Sometimes you need to pencil straight, parallel lines along the axis of round stock, such as when you align spindle holes on a dowel rail for a chair back. This can be frustrating without some kind of jig.
On a flat, smooth work surface, snug together the round stock to be marked and a thin wood strip. Draw the first line on the round stock along the edge where the two pieces meet. (You may need a helper to hold the pieces together while you mark the stock.) Rotate the round stock to draw other parallel lines at the desired spacing, as shown.
—From the WOOD® magazine shop