The legendary Cardboard Box - Big Boss Tier
Sneaking under the box will make you significantly less detectable, and moving around will not effect your stealth. However once you enter the Caution or Danger stage, the box will be removed until you're hidden

JUST the box, nothing tactical about it. Feel free to add your own effects to it if you wish.

The legendary Cardboard Box - Solid Tier
This version will add sneaking benefits to your character while under the box. Sneaking and remaining still will hide you, but you'll be more noticeable while moving.