Two of the hooks and the end-clip had snapped off the right-side plastic strip embedded in my '82 240D rear bumper rubber. A PO had tried to glue it, but it came loose anyway and looked like crap. I ground the jagged plastic stubs of the hooks & clip down flush with the plastic strip and drilled 7/64" holes at the center of each spot. Then I used 3/4" #8 sheet-metal screws and fender-washers to re-attach it to my bumper. It's probably stronger now than the original setup.
For now, the left side seems still solidly attached so I'll wait to deal with that someday when/if it comes loose.

Happy Motoring, Mark

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DrDKW