No doubt you've seen the trim-head screws. They use a #1 square drive (Roberts I think they're called) head, about half the diameter of a Phillips head. I buy huge boxes of the stainless variety - very useful for outdoor applications.

The smallest black ones are pretty small. Best to use a large predrill bit, just a tad smaller than the threads as they'll strip or break easily if the predrill is too small.

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1986 300SDL, 362K
1984 300D, 138K