Thoughts
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.