This is a bench dog for the Harbor freight 60" workbench (http://www.harborfreight.com/60-inch-workbench-93454.html). This bench dog provides for a 1/4-20 nut. I use these for strapping down benchtop machines and for various jigs. (example hardware: http://www.leevalley.com/en/wood/page.aspx?c=&cat=1,43455&p=61994)print hex slot up on 0.3mm, 3 shells, at least 15% infill