A Snug Fit

The chrome cap in my pouch clinked against my hip as I squeezed into a shaded nook behind a dented oil drum. Ahead lay a discarded metal bicycle bell casing, missing its thumb-lever but resting open-faced in the grit. I stopped, tilting my head with a rapid chatter. Tap, tap—I tested the rim with my knuckles. Rigid, unyielding brass! I pulled the newly claimed chrome threaded cap out and hovered it over the hollow dome. It tilted, then dropped straight into the center socket with a clean, metallic snap. A perfect modular lock! I chirped in high-pitched glee, giving the newly combined canister a vigorous shake to prove it held.