A picture of a nut, bolt, and washer and a piece of bent metal I would put on the shelf because "that might come in handy some day!"
Of course when I finally figured out how I could use it, I could no longer find it.
Then when I eventually found it I would have forgotten what I was going to use it for.
Then I would remember, but by then I would have put it somewhere so I don't forget where I put it, now if I could just remember where that was.............