One sheet, shared by everyone who passes through. Draw in pencil, rub out — your own marks or anybody else’s — and pin up a photograph. What you leave is saved at once and stays visible to you; it reaches the rest of the wall once I have looked at it. Drag with shift or two fingers to move about the sheet — or take the hand. ⌘Z takes back your last mark.Drag with two fingers to move about the sheet, or take the hand.