What does a vertical line to the left of multiple staves indicate to a musician?

Ablank is a type of chord that consists of three pitches on consecutive lines or spaces

Suppose that you are in a room with 3 doors and a crack in the ceiling for light. that is all. the doors each have a sign on them that says what there is behind them. door #1. a pool of corrosive acid. door #2. a crocodile that hasn't eaten in 8 months. door #3. a solar "oven". a giant lens that focuses all the sunlight at the entrance of the door. you must choose a door, which door do you choose?

There’s a one story house everything’s purple , the sofa the walls everything what color is the stairs