Use a stitching awl to punch holes in leather along the stitching line. This tool resembles a small ice pick and comes in two parts: the awl (needle) and the haft (handle). Look for sets that include interchangeable awls of various sizes.
Place the leather on a flat work surface. Use a ruler, a straight or curved edge and a pencil to measure and mark a stitching line.
Use an over-stitch spacer to make evenly spaced indentations along the marked stitching line. The over-stitch spacer consists of a small metal wheel attached to a wooden handle. Small, evenly spaced points protrude from the wheel.
Press the wheel portion of the over-stitch spacer firmly into the leather and roll it along the stitching line. Keep the pressure on the leather constant. The resulting indentations in the leather are the points to be punctured with the stitching awl.
Punch through the leather with the stitching awl. Use a controlled pressing action instead of a stabbing motion to penetrate the leather. You will need to lift the leather from your work surface so that the awl can penetrate the underside of the piece.
Withdraw the stitching awl once the point has completely penetrated the leather. Avoid pushing the stitching awl so far through that the handle touches the leather's surface. This results in a much larger hole.
Punch one or two holes at a time and stitch as you go. The awl has a flattened blade that spreads the leather as it punctures it. Left for an indefinite period of time, the leather will begin to contract, and the punched hole will become narrower and more difficult to stitch.
Use a sewing machine and a wedge-point needle to stitch most garment-weight leathers.
Keep the stitching line approximately 1/8 inch from the leather's edge.
Use a compass or wing divider to mark a curved stitching line.
Make sure that the appropriate wheel is attached to the over-stitch spacer. Most spacers come with interchangeable wheels that will produce five, six and seven holes per inch.
Guide the over-stitch spacer along a metal edge as you mark the stitching line. Avoid pressing the stitching awl into the work surface. This will damage the awl's point.
Rub beeswax every one or two holes when punching through very thick leather. This will ease penetration.