Here we have a nice shot of the damage caused to the terminal when my meter's probe slipped off the top of the nut and shorted against the base of the terminal and that aluminum angle piece to the right.
Clearly, I couldn't leave it like that. Being as clumsy as I am, it's bound to happen again as long as that aluminum perches so dangerously close to those terminals. I can't move the angle aluminum because it's what's holding the batteries in the car. I figured the best thing to do was to put some sort of rubber insulation on the aluminum to keep any accidental shorts from occurring. So, I went down to the local hardware store to look for a sheet of rubber. What I ended up finding was a sheet of PVC used for lining the floor under a shower pan. Waterproof, flexible, and more importantly, electrically non-conductive. It's sold by the linear foot, and one foot of the stuff cost me less than $6.
I cut a few carefully measured strips from the sheet and painted some contact adhesive on one side.
I masked off the angle aluminum as best I could and painted those with the adhesive as well. After a couple hours of drying time I carefully stuck the strips to the aluminum.
It stuck on very well and should do the job. I had cut the strips so that I could wrap them around the bend, hoping that the sheet would stick to the inside edge's 1/8" surface of the aluminum. But the material simply isn't flexible enough to make that bend. If I could find a sheet of real rubber, and if it were thin enough, it would make that bend, but I think this will work fine. Take a look, there's no way to short the terminals against those aluminum pieces by accident.