The right side skirt has an ugly and badly rusted dent from a long-ago car-jack mishap.
Here, the battered section is already cut out.
Fine occasion to have a look at the interior: No rust!
The edges are cleaned and painted with zinc spray (which is debatable).
A matching section is cut from a replacement side skirt. Its edges are joggled for a better fit, and perforated. Unfortunately, the sheet metal of the replacement part is thinner than the original, a part from a donor car might have been better.
Finally, the replacement part is welded in. I admit that the welds could look better - I had my difficulties welding “upwards”…