UPDATE: NEW UPLOAD that has four clamps grouped together. These will fit on a 120mm x 120 mm build plate.
This is a reversable hold-down clamp used on work surfaces with t-slots. Use with thin work pieces one way, or flip around to fit thicker stock. This is based on a collection of different clamps I've seen while browsing woodworking tool retailers.
The way the original file is oriented, it just barely fits on my TOM. Feel free to test another angle or gang more together.
I printed mine with 3 shells and 50% fill. They seem to be holding up good so far. This is designed to work with 1/4" - 20 bolts. 3" long works well, but use whatever length fits your situation.
The knobs in the pictures are store bought (already had them). I plan on designing a printable knob with nut-trap in the future.