...individual game systems vary, but fifth-edition D+D was designed with many mechanics which depend upon open rolls with secret modifiers: if your players' characters can perceive an action taking place, roll openly; if they can't, invert the roll (DC-12 modifier) and roll secretly against their passive scores...
...hormones and time, mostly: i haven't been able to pull off that look for thirty years and trust me when i say that you wouldn't want to see me try...
...individual game systems vary, but fifth-edition D+D was designed with many mechanics which depend upon open rolls with secret modifiers: if your players' characters can perceive an action taking place, roll openly; if they can't, invert the roll (DC-12 modifier) and roll secretly against their passive scores...