You're talking about these:
Which tend to be associated with the military. Most people outside of the armed forces have never heard of these things, but they do their job remarkably well.
I got those exact ones, in white! You ain't kidding. They feel quite strange at first, but boy do they ever work. I jumped over a railing today as I was walking at lunch, and my shirt stayed as tucked in as when I put it on!
I feel like someone could beat the crap out of me and I'd still look pretty sharp.
They will both place one's getting laid in jeopardy, but for different reasons. It just depends on whether you want to not get laid because you look like a british grandpa or because you are wearing some unidentifiable elastic contrivance under your pants.
Hopefully it's a done deal by the time I take off my pants