ELNikkor wrote:
The best way to find out what it is for, is to throw it away. In three days, you will not only find out what it is for, but you will have to go out and buy one just like it, or the expensive thing it goes on won't work at all! (Just my experience, probably no one else's...)
My experience is only slightly different. I often find out in less than 3 days, but with things I've puzzled over for a very long time it can extend to about a month. Invariably it's cheaper to buy a used replacement of the expensive thing than to track down a replacement part. If I do hang on to the unknown bit I don't find out what it fits for many months by which time I've forgotten where I stored it...
This is IMO the most common variant of Murphy's law.