Every bit of it was covered in stamps except for a square inch on the front, into which Mrs. Weasley had squeezed the Dursleys' address in minute writing.
They set noiselessly to work, and the Parsee on one side and Passepartout on the other began to loosen the bricks so as to make an aperture two feet wide.
A thundersheet, in case you don't know, is a thin piece of metal, a couple of yards square, which when shaken produces a mysterious rumbling noise not unlike thunder.
There was a pane of glass, about six inches square and made to slide open, through which the pilot, by turning his head and stooping slightly, could communicate with his passengers.
Then she examined her cell. It was a chamber about six feet square, with a small window and a door on the slightly sloping plane of the roof formed of flat stones.