This is a design for a wrench with all the sizes for a standard ETC C-clamp. It seems to be holding up so far, the next step is to make a bunch and hand them out to the theatre lab kids and see how many come back broken. If you break one, or have suggestions for the design, leave details in the comments. Update: I've revised the design to be slimmer and lighter, and I've also increased the size of the hole in the handle. The file for this version is labeled v2. I've left the old one up for now.The one I made had 3 shells, 50% fill and a 2mm layer depth. Took about an hour. Seems to be sturdy, and is holding up so far.