zero "puck" holder for CNC3-3018Pro

at our makerspace we have a CNC3-3018Pro which we use for milling PCBs. For Z probing, we use a "puck" which we put on the PCB to make a circuit when the tool touches the PCB. This "puck" needed a holder, so I used FreeCAD to design such a holder, and printed it on my 3D printer.

Not perfect, but good enough.