I saw an episode of Ask This Old House about a month or two ago. During the show, when they preview new and different tools, they featured a tool that receives a can of spray paint and has a wheel with a dial that would allow you to adjust length. In the end, what happened is you roll the wheel down a log that you wanted to saw for fire wood and depending on where you had the distance dial set it would shoot a dot of spray paint every 16", for example, so you would know exactly where to cut the log to get the perfect sized wood for your fireplace.
I would love to have one of these, but I've been unable to find one. Any help you could give me to assist in finding this would be greatly appreciated!!!
Re: Cutting Wood
A cheaper and faster method will be to measure your saw's length, and mark it at your desired firewood length. From there you simply set the saw on the log, eyeball the cut mark, then move into position and have at it.
If you really need the direct method, then a scrap of 2x4 and a can of paint will do the same thing, you just walk along, marking the length of the 2x along the length of the log.
By the time you've cut 1/2 a cord of wood, or so, you should be able to pretty closely eyeball the length without any need for marking at all. Good luck, be safe.