Assembly Assistance for the Printrbot Simple - 3D Printing: Build your Own 3D Printer and Print your own 3D Objects - page 54

Figure 3.16 All the wires from the motors will eventually connect to the mother-
board.
Now it's time to attach both Y-axis mini-assemblies (1 and 2). Find the small nut
that fits the lead screw. Slide the Y-axis Mini-Assembly 1 over the two 10” metal
rods so that the lead screw comes up and through the cutout in the shape of the
nut. Stick the nut into the hole and thread the lead screw into it. Make sure the nut
stays in the (nut-shaped) hole, because you then use two M3 bolts to lock that nut
into place, as shown in Figure 3.17 .