The inverters for the photovoltaic panels need to be fixed to the rails on which the panels sit to protect them from the weather. The fittings they sent originally were not correct and they have sent replacements but they all need to be drilled so they can be screwed to the rail (the three large holes are for the inverter).

I tired to do it manually but broke so many drill bits I decided to invest in a small, table-mounted, vertical drilling machine and did it at the rental house. Took a while but all 36 plates are now done.