Use these STLs as is - one is a bracket for the usbpicprog card (untested) (print two), the others are generic left, right and center PCB holders, print however many of whatever you need.Or use the SCAD file to generate custom brackets to fit different PCB sizes and mounting situations.You can use the "inner" parameter to make the screw bit go UNDER the PCB - but if you want that on both sides you'll have to leave a corner open or perhaps bend the plastic out to get the board in.