Marking and drilling holes

Fig 1: Identifying Holes And Drill Bit Diameters

Courtesy of VOLVO CARS OF NORTH AMERICA.

Hold the guard plate securely. Carefully mark out the holes for the six screws using a pointed object through the holes in the guard plate
Remove the guard plate. First drill out the hole using a Ø6 mm (15/64") diameter drill bit. Then use a Ø12.5 mm (1/2") diameter drill bit. Drill at right angles to the underlay. Do not enlarge the holes excessively or the rubber nut may not sit properly
Remove the filings. Clean around the edges of the holes.