When I joined Microsoft, I had a brand new computer waiting for me. One of the rites of passage for new employees is setting up their computer. A colleague helped me out with this effort, and one of the steps he performed was installing the network card. (Back in the day, network adapters were not integrated into the motherboard. If you wanted one, you had to buy an add-on card.)
Now, when you install a network card, it occupies a slot, and you need to remove the corresponding slot cover because the card comes with its own integrated slot cover. When my colleague removed the old slot cover from the computer, he didn't just toss it into the garbage. He folded it back on itself with the tab on the top, like this: ᔪ
What the heck was that all about?
He didn't give me time to ask the question because he immediately walked over to my office door, pulled it all the way open, and then jammed the doodad under the door. The tab at the top caught the door, and the angled bottom part dug into the carpet, holding the door open:
In other words, he took the slot cover and converted it into a doorstop.
Thereafter, I noticed that all of my coworkers used slot covers to hold their office doors open. It was part of the team's tribal knowledge.
(This trick is lost to history not only because computers nowadays come with all the peripherals you would typically need, but also because the new office doors are not spring-loaded.)