David Macaulay’s How Machines Work uses pop-ups and award-winning illustrations to demonstrate the technology of six simple machines. Follow the mad antics of Sloth and his side-kick Sengi as they try to break out of the zoo with the help of levers pulleys screws inclined planes wedges and wheels. Brought to life through pop-ups and pull-outs meaning you can explore six simple machines from bicycles and cranes to hammers and drills through interactive science. Packed with engaging hands-on activities David Macaulay’s How Machines Work will gear kids up for scientific and engineering greatness! Toy Safety Information. Not suitable for children under 7 years of age.