In the spring of 1963, newly graduated from high school, I shipped out to Idaho by Greyhound bus to cut timber in the Targee National Forest to earn college tuition. The job involved being dropped in the forest with fuel, oil, food, a Homelite chainsaw, fifty feet of chain, and a File & Joint Chainsaw Sharpener.
This sharpening guide became my lifesaving daily routine. Clamping on the bar, setting the angle and depth to file, four strokes each tooth, and magic the next day as the Homelite XP1000 sliced and diced 300 trees!
I still have and use the same sharpener today, and I am pleased that the new ones are exactly the same today, keeping all teeth identical for smooth, even cutting.