Cartoon adventures of builder Bob and his friends, Travis the tractor, Scoop the bulldozer, Lofty the crane and Dizzy the cement mixer. When Bob's new electronic organiser goes wrong, he ties knots in his handkerchief to remember what jobs he has to do. However his system soon breaks down, and he goes round doing the wrong jobs. He finally admits to Wendy that his organiser is broken, and Wendy reminds him what his first knot was for - to buy new batteries.