Step 4 - Assemble the Mirrors and Base Plates Step 4 - Assembly Simple and Quick Step 4. Bring out the trusty Fiat Screwdriver and screw the Base plate and Mirror together using the provided Screws (silver in my case). Voila, your M3 is ready for fitting. Next page: Step 5 - Fitting the Mirrors Previous page: Step 3 - Align Before Fitment