If you are sharpening a chainsaw manually, you should always sharpen a chainsaw in the direction that the file only grips in the forwards stroke. You can lift it slightly when pulling it back so that you don’t go in the wrong direction. A chainsaw will have two sets of cutters on the chain - both going in opposite directions. For this reason, you’ll need to sharpen it in both directions to ensure that the chainsaw is completely sharpened by the end of the task. To make this easier, mark the first tooth that you’re going to be sharpening with a permanent marker. File this tooth up to 10 times, then move to the next tooth. However, the next tooth you’ll be sharpening won’t be the one next to the first - it’ll be the one afterwards. So, sharpen every second tooth until you reach the original one that you started with. Once you have finished the first set, turn the chainsaw around and start filing the teeth that you missed out. If you don’t want to mark your chainsaw, most models will have one tooth that is slightly different from the rest as a way of the manufacturer telling you which to start sharpening from. This can sometimes be helpful, but most of the time the manufacturer’s marker is too difficult to spot. However, if you really don’t want to mark your machine, make sure to look out for this while filing. Once you have finished these teeth, you will be left with a completely sharpened chainsaw ready for tackling whatever project you are working on next.