Sitting on the toilet, he adjusted the small rug for the thousandth time. It looked square, but no matter how he set it against the bathroom tile, one of its edges always diverged from the lines of the square tiles. Fed up, he dragged the rug out of the bathroom and measured it with a T-square. It confirmed what his eyes said: The rug, with its stiff edges, was truly square. Now questioning, he took the T-square into the bathroom. The tile also measured as square.
Back in the bathroom, he measured rug and tile against the T-square again, with the same results. But lined up against each other, the edges diverged. Squinting, he leaned in close and looked close at the space between two diverging parallel lines. He saw distance, some manner of perspective that shouldn't be there, shouldn't be in a sliver of tile two inches from his face.
He probed it with his fingers. His fingers, then his hand, kept reaching into that crack that shouldn't exist. Excited, he pushed the rug out of the way. And he screamed as the interaction between rug and tile that opened that unreal geometry vanished, and with it his hand.