If it turns out to be one of more Flex Discs be sure the Mechanic does not put on some made in PRC Flex Discs.

Card Board is good insulation to lay on and Harbor Freight sells some Foam Mats for walking on. Sort of antifatigue Mats.
I use at least one of the Mat Squares when I get under the Car.

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84 300D, 82 Volvo 244Gl Diesel