The ten basic paper engineering mechanisms shown in this book have an almost explosive quality. Each 'up-pop' folds flat, but when it is eased out of its envelope, or restraining sleeve, it suddenly and unexpectedly jumps into a 3-dimensional shape. This element of surprize is most attractive and suggests all kinds of imaginative designs. The motive power for each mechanism is provided by a single elastic rubber band. With each example there are useful notes about the mechanisms and suggestions for the further development of the ideas to create original designs.