This is a coupler for adding extra extension handles to your paint roller. The ones that came with my paint roller broke, so I designed this replacement. For standard paint rollers, you should just be able to load the STL file and go. If you need to customize it, you will need the Screw Libraries Created by aubenc ( http://www.thingiverse.com/thing:8796 ), plus the SCAD file I have provided. Print it, and then screw it on to the ends of the extension handles.