Play the episode 'The Builders' from the 1st series of Fawlty Towers. About 16 minutes into the epsiode, Mr. Fawlty realises that the Bilders have blocked off one of his doorways. Manuel enters and Mr Fawlty bangs his head against the new 'wall'. If you watch, you can see the cardboard used to immitate a wall break away and move. Not a very impressive wall!