A Psych Prof is talking about tacks.
Prof: Easy to push in, hard to pull out... because when it was being designed, pushing it in was what the designer had in mind. That's what it's for - going in. Pulling it out is the thing that nobody thinks about. It's the thing that you don't think of as the actual function.
Later in the same lecture, the Prof is describing scissors.
Prof: There's a big hole and a small hole, so you put your thumb in the one hole and you put two fingers in the other hole. But for some reason, this time, both holes are the exact same size, and my fingers don't fit in properly! I'm going to injure myself!
Time passes. The Prof is describing pumping gas.
Prof: If you end up on the wrong side, you have to pull the hose way out and all the way around in order to stick it in the hole.
-- Applications of Psychology lecture, overheard by Deanna