Motors and Movement - Printing in Plastic: Build Your Own 3D Printer - page 218

Figure 13-8. Tighten the nuts to hold the motor mount securely.
Insert two 4” machine screws, as shown in Figure 13-9, and secure them in the same manner as the
other two 4” machine screws. Use two nuts on the inside that will be tightened against the motor mount
and the inside wall of the Lower Structural side and a single nut to tighten against the outer wall of the
Lower Structural Side.