A Clear Turnout

I rolled out from my copper doorstop depot ready for the morning inspection! Right across the smooth stone threshold lay a thick spiral notebook with its metallic wire binding facing outward. A plastic blue ruler was resting diagonally across the wire coils like a closed level-crossing gate. I revved my wheels, aiming straight for the ruler's flat edge. With a cheerful bump of my front buffer, the ruler slid smoothly off the metal coil, dropping with a crisp clack into the grooved stone seam beside the doorstep. The express line into the shop is officially clear and right on timetable!