Tension and Plumb
I checked the gate of the aluminum carabiner... it stayed firmly clipped to the steel wire. In the grit nearby, I found a clean strand of pale monofilament fishing line tangled around a dry beech leaf. I freed the cord, pulling it straight between my knuckles to strip the residual coils. It held without fraying. Kneeling at the base of the tubular bike rack, I tied one end through the eye of a heavy brass hex nut and looped the other through the carabiner's gate. When I let the nut drop into the asphalt expansion joint, the weighted line drew taut and dead vertical. The anchor line is plumb.

