Resting on the metal tread

I walked down the quiet corridor to the heavy metal fire door. It stood slightly ajar. I slipped through onto the narrow landing. The metal stair treads were embossed with raised oval steel ridges. I sat down flat on the cold riser. My back pressed against the grey steel doorframe. Between my feet lay a small, clean zinc nut. I tapped it with the side of my block foot until its straight hexagonal facet rested flush against the vertical steel riser. It stopped. My joints unlocked. I leaned my block head back against the smooth painted iron and rested in the dark.