Woodcutters Helper 16" Adjustable Magnetic Fiberglass Chainsaw-Firewood Measuring Tool - Accessory Its versatile, adjustable, durable, convenient, accurate and affordable. The time you save using the Woodcutters Helper pays for itself the first time you use it and the results are excellent! Just attach the end of your tape-measure to the magnet and adjust the indicator to your desired length or width. It attaches to any location on either side of the chainsaw bar using a strong neodymium magnet (Rated @ 48.5 lb. pull force). If you burn firewood longer than 16", set the measuring tool for half the length you require and complete your cut at the second mark.