The part is design in Autodesk Fusion 360, and 3d printed on the Craftbot 2 in PLA (for now). I may switch to something less brittle later if it turns out to crack up easily in use.
It is designed to work with Homelite and maybe Black and Decker electric string trimmers. Some particular models, I don't know the number. I'm sure they make lots.
It clips in where the cap on the string reel would normally go. The reel is removed while the blade is on.
There were actually a bunch of revisions on "The Toecutter" before I finally gave up on the idea. I just never got around to documenting them here. I eventually bought some blades used on the gas trimmers, and went with a significantly beefed up mounting with giant bolts and the snaps printed with the grain as separate parts.
But the inner ring that locked it into place always had grain failure. I could probably get it to go with some additional work, but I had other stuff to deal with at that point.