In the military, we would “pull colors”, meaning hoisting and lowering the flag on base, morning and evening. I only got to do it once that I recall. But if you’re outside at “colors” you stop, turn towards wherever the base flag is, and salute (they broadcast the calls) if you’re in uniform. If you’re in civilian clothes you just put your hand over your heart.
Well, this isn’t the flag, but it’s more universal and pretty much stops everyone in their tracks, even if they don’t salute (although honestly, doesn’t it kind of make you want to?). You have to be quick, the colors don’t last long.