

That’s basically what they are doing now. Fun fact, TSMC the company that manufacturers the most advanced chips in the world actually rigs their machinery to explode if they where to ever be invaded by China. Just to be clear, this is a real thing and not a joke.
Sewer cleanout probably. Never seen a cap like this before though, looks kinda flimsy. Maybe get a piece of plywood and cutout/drill for holes that align with the nubs and turn the plywood so you can put force on all four nubs?