Similar to tools that can be bought online for $15-$30 this simple 2-part print can be used to balance the standard Honda mulching mower blades when sharpening them. The two seats should match the holes in the center of the blades. If you have a different blade size feel free to comment with the size and I'll try and get it added, the more blades supported the better.

You can find videos on YouTube about how to use this type of sharpener, e.g. this one, note not my video.