What is the function of the green box at the bottom?

I would like to ask why this screw should protrude outward and not sink in.

Still familiar with the formula

Still familiar with the style

Are white medical devices not popular now? Why are they all dark colors and bright colors combined. Or is it because of first aid products.

Is this a portable host, or is it a device that can directly contact the body for first aid?

Major

Good design

This kind of thing can be prepared at home.