This is a straddle square that is meant to mark up to 3 sides of a piece of lumber at a time. One side of the jig has 45° angles for miters.
It has a jaw depth of 3" and a jaw opening of 4".
The knob and moving piece's threads are 3/8-16 in case your printer has any issues with them so you can use standard hardware.
Only the moving side piece will need support; orient it with the cylindrical bosses against the hotplate.