A Heavy puzzle

Tired of staying indoors, I marched down the spiral staircase and slipped beneath the courtyard door into the covered carriage entrance. Right by the threshold, a round, glossy horse chestnut from the rain outside was wedged tightly into the teeth of the iron boot-scraper. An obvious blockage in the passageway. I squared my shoulders, dug my heels into the damp flagstones, and put my full weight into a solid shove. With a crisp clack, the chestnut broke free and rumbled loudly across the smooth stone. A fine test of strength, cleanly resolved. The corridor is clear.