Those nice carpet floor mats that came in my 1999 s420 were getting to be a pain as after a while they start to bunch up and they just won't act right.
I was exploring some way to stick them down, but every method I considered would most likely make a mess of the carpet underneath.
So...
At the office supply store I bought the cheapest chair runner I could find ($15). This is the kind that is a clear plastic material with little hobbnails to grip the carpet underneath your office chair. Cheaper is BETTER as they are not too thick (cut with regular sissors) and they bend very easily.
I cut the pieces to size (easy to trace because chair runner is clear) and used contact cement to glue 'em directly to the underside of floor mat carpet.
Terrific! The floor mats no longer bunch up or creep...and... if you spill stuff on them it doesn't go through to the real carpet...and ... contact cement is waterproof so you can wash your mats as often as you like.
I'm sure I'm not the only one with this problem.
KM/Nashville