These are different solder pads that can be used in wiring of an electrical project. You can connect wires with spade or ring terminals together or wires that are soldered only to the pads or a combination of both. Like the wire clamps shown above I print the solder pads on rafts and more than one at a time. You can find the files to print this on my thingiverse account ( HERE ). You can find all the files to 3D print this object and others on my thingiverse.com account ( HERE ). A link to the solder pads on my web site.... http://1fatgmc.com/RailRoad/3D-Printer-2/page-55.html One could also copy this idea without using the 3D printed part by using just the printed circuit board alone. Sumner