The side plates of the mecanum wheels had to be very precisely manufactured. That is why I designed them in Autodesk Inventor, and had them manufactured by a CNC mill. Each one took about 45 minutes to make, and I needed 8.
Once they were out of the CNC mill I made this jig that would help me bend each one of the flaps at a 45 degree angle. The grooves on the bend points were made by the CNC mill to help me bend the plate.