This is used to plug 20mm dog holes on MFT style table. Prevents hardware and dust from falling below the benchtop. I designed in Tinkercad. I built in a pause to allow inserting 6.0x1.8mm round neodenium magnet. I reamed my dog holes using the Parf dog hole reamer to allow the plug to fit loose enough to allow removal with another magnet. There is a slight rim on top of the plug to prevent falling through, so hole must have a slight taper to allow plug to fit just below bench top surface. The .stl file is a single plug and the .3mf file has 16 ready to print with mouse ears, they are easier to remove than outer brims. 

Enjoy!