The squarish metal thing that the latch on the door strikes and latches onto. You can loosen the four Allen head screws that hold it on and move it a little bit outboard to help get your door to close. The one on the driver's door of my 240D got a little loosen and migrated inboard causing my door to require slamming to close before it got to the point where it wouldn't close at all. Ten minutes with an Allen wrench fixed it. I think it's a 5.5 or 6 mm.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.