This is my comment from the other topic on fuel cap chains, but I will put it here.
"I was in the fueling business for eighteen years. Just lay a nice towel on the wing and place the cap on it. You can then use both hands on the fuel nozzle. If it's windy then do as you need. The towel then comes in handy in case of a spill on your paint.
Also, carry a pair of leather gloves in your plane. That way you won't rip your hands open on the grounding cable. And your hands will stay clean. A lot of those hoses are quite dirty."
We had some mats that were a heavy rubber. Almost three-sixteenths of an inch thick. We hated them. They were okay if you had a ham-fisted employee. They are great for sitting on as you need to do to fill the inboard tanks on airplanes like King Airs. Make sure they are wiped down first. I would not recommend one so heavy in my baggage compartment. I was always concerned that any dirt on them would scratch the paint as the employees sometimes slid them on the wing. We also had some that were like tool chest rubber mats. Similar to the material you might use to organize your rollaway tool chest. We also had some that were more open like a net. I didn't care for them as the cap could drop an edge into the open space and hit the paint. The lighter weight ones tend to blow around in the wind. For light planes I always just used a nice towel. The towel helps you cover the hole if it's raining too. I would recommend always being there or fueling the plane yourself.
Years ago, we bought a cheap yoga mat (probably at Walmart) and cut a hole in it the size of the fuel cap opening. Used it for years on the DA-40's, the RV-7A and plan to use it on the RV-10 when Jonathan let's me have it back
Don't know how fuel resistant it really is, but years of some spillage does not seem to have disintegrated any of the foam. It is a little bigger than an airplane specific mat, but you could probably cut it in half and make two.
I have been using a silicone cooking sheet for both my Waco and RV. It is thin and fairly durable. It seems to take the odd fuel splash well. I cut a hole the size of the tank filler hole about 2 thirds the way up in the sheet. This allows a bit of over hang on the leading edge. I also have a small dish towel ready for any spills.
I personally don’t like the fueling mats. They seem to collect dirt and then that dirt ends up scratching the pretty paint. The fuel cap is carefully placed on the ground bottom side up in front of the tire rather than sliding off the wing. I almost always fuel the airplane myself even at the big expense FBO’s. I say almost always because I’ve allowed someone else to fuel it two times in 1800+ hours.
I dont use them on my polished wings. And I ask line folks to avoid when I remember. Got back from a recent trip and saw scratches in the skin around the fill hole. Will probably polish out.
I bought a silicon pet water/feeding mat and cut a hole in it. I use it all the time fueling - it’s super light, rolls up compact, and has a raised edges, preventing the paint from getting scratched and hit by fuel. Less than $20.