Wendy goes to JJ's yard with Lofty and Dizzy to collect a steel joist. Lofty is nervous about carrying the joist, but Dizzy and Trix race off with the bricks and mortar, while Wendy stays behind to sort out a problem with JJ's printer. Lofty approaches a bridge with the joist when Dizzy and Trix hurtle past and startle him. He bangs the joist into the bridge, damaging the brickwork. The Machines try and repair things, but their attempts at bricklaying are far from successful. Bob wonders where they've got to, as he can do no more until they arrive. Wendy returns and is surprised to find no Machines, so she goes back to investigate. She finds them at the bridge and repairs the brickwork properly. Lofty continues on to the Bentleys' and, with increased confidence, maneuvers the joist through the door on his own. With a team effort, the job is finished and Mr Bentley is delighted when he returns - though not so happy when he finds that Bob has eaten all his biscuits!