Bad Ideas explained: http://www.furaffinity.net/journal/321008/ Includes index.

It's a sort of cupless cup - and an anti-cup.

In some places, you see a rubber cup on a wall, at just the level of the doorknob. Thus if the door swings into the wall, the knob hits the rim of the rubber cup and the knob doesn't damage the wall and the wall doesn't damage any locking mechanism of the doorknob. It's nice, simple, and solves a couple problems quite well.

What it doesn't do provide for female fun at male's painful expense, so let's modify the building some. The wall now has a panel.. or two. A sort of tiny lunette, perfect fitting the neck of a scrotum. Guy on one side, his balls on the other. And his balls are at just the height of the doorknob. Whether he has to stand in a 'well' or on support, his balls will be at the right height. Is there also a window so his head can be seen? Maybe, maybe not.

But now if the door should be opened with great haste, instead of a dull bounce off of a bit of rubber, there is an exciting painful nutshot from the doorknob. And if it should be a windy day as things are brought inside, or someone enters after bad day or such, well... there could be several blows.