Above the empty auditorium

The upper gallery had been closed for years, but from the stalls its front rail still looked straight and polished. On the inspection platform, Mara placed one hand on the rail and felt it tremble beneath her fingers. Behind it, one iron bracket had pulled away from the wall, leaving a gap wide enough for her pencil. A hairline split travelled outwards from the final bolt. Nothing had fallen, and the red seats below remained perfectly arranged; even so, she spoke quietly as she ordered us back through the door.

Select two words or phrases from the passage that suggest the upper gallery is unsafe. Explain how each selection shapes the reader's impression of the danger.