14-20 inch Chainsaw Teeth Sharpener Saw Chain Blade Fast Sharpening Stone System

I don’t know whether this product works, as there were no instructions on how to use it. The item came in an unmarked bubble-wrap bag (not in any kind of sealed packaging even saying what it was, which makes me wonder whether this was intended for retail sale). Considering that this item is intended to be used with what can be a very dangerous tool (a chainsaw), some instruction for proper and safe use is necessary.