On Tue, 12 Sep 2017 09:25:26 -0400, micky
wrote:

Some of the screws I use are not attracted to magnets. What are they
made of?

The last bunch were heavy duty sheet metal screws, that came with a
license plate frame, and I kept dropping them behind the grill, and the
way the plastic bumper is made, they don't fall out. And my magnet on
a stick didn't work!
Most likely stainless steel, but also possibly plated brass ot
aluminum.