To start, line the template up on the sheetwood, and using a single edge razor, slowly trace the rib template with the razor blade. Use the template as a guide, and try not to press against it too hard or the razor may cut into the template as well and ruin your template. If you find cardboard too weak, a thin sheet of 1/64" plywood (from a hobby shop) would also make a good rib template as well, plus you can cut the plywood with a good sharp pair of scissors. After the first cut you should have the following:


Now to cut the first rib, slide the template down until the amount of wood above the wood is equal in size to the height of the stab rib drawn on the template (see above picture). To cut the rib, just trace the edge of the razor along the template as before and the rib will be cut. Because the wood is fairly thick, it may be easier for you to cut each rib in two cuts. The first cut will be about half way through the balsa wood, and the second cut is like the first except it cuts the rest of the way through the wood. This 'two pass' cut method will help keep the wood from splitting when cutting the ribs, which may be a problem if the wood is too hard. Keep on cutting ribs until you have at least 7 ribs. I usually cut an extra rib or two because I usually break one or drop and loose one.