This is a surface cam clamp to hold stock on a workbench.
The more you push against it, the more it holds the stock; this is ideal for hand planning small pieces.
The clamp is to be coupled with a 20mm metric bolt, that will fit a 20mm hole in the workbench.
There are a left and a right version, but one piece is sufficient to hold firmly if you already have standard holders.
Mines are printed in PLA, at a Z resolution of 0.22mm.
I tested infill ratios between 15% and 25% with success.
Once printed, a non-slipping material should be sticked to the spiral face.
I used strips of air tube and thin double-stick tape; this worked well so far.