This came to my attention as I drove to or from work(can't remember which) on a rainy day. It made itself plain when I pushed on the brake pedal, heel on the floor, and my heel went through the floor with a bit of a crunching sound. Highly disturbing, I assure you. Especially when I looked down and saw a hole, and wet pavement. Let's say that, combined with other worries, the word 'despair' comes to mind.
It stayed rainy for a day or two, so all I could do was bend a piece of sheet metal to rough shape and put it under the rubber matting.
Once it dried out enough I found that a whole section of the floorboard was rusted out, right under the pedals. The proper repair would be to cut out the rusted section, weld in new metal and coat it. No welder, knew nobody with one, no money to pay for repairs. So I cut and scraped out all I could of the damage, coated the edges and surrounding area with- y'know, I can't remember what? May have been roofing tar- and then shaped that piece of galvanized sheet steel to fit pretty well and used more of the sealant to lock it into place and- hopefully- prevent water from getting inside.
That patch held nicely for the next couple of years, at which time the Courier went away. Short version: was at a point where the cost of getting another- newer- vehicle was much better than trying to keep it running, especially with parts availability being what it was.
Amazing the repairs that come to mind when have to think of something