Winding Around explores the benefits and uses of the screw. RobbO and RobbEE learn how to hold materials together using a screw, and how to use it to lift up loads and raise water.
Pressing Down explores the benefits and uses of the lever. RobbO and RobbEE learn how a lever can be formed in three different ways to do different kinds of worklift and lower, separate, and open.
Pulling Up explores the benefits and uses of the pulley. This clever device uses rope wound over a grooved wheel to help lift heavy loads. RobbO and RobbEE use a pulley to remove the engine from their car.
Rolling Along explores the benefits and uses of the wheel and axle. RobbO and RobbEE build a cart to make it easier to move a heavy load, and learn how the wheel and axle are also used for lifting and turning.
Sloping Up and Down explores the benefits and uses of the ramp. RobbO and RobbEE learn that a ramp is called an inclined plane. They discover that ramps are used for building stairs and escalators, and were even used as far back as ancient Egypt to build the pyramids.
Splitting Apart explores the benefits and uses of the wedge. RobbO and RobbEE need to build a wedge-shaped machine to move the snow piled outside their workshop. They find lots of other uses for a wedge, too.
Readers learn how this simple machine makes it easier to move things to different levels. They learn how flatter slopes use less effort than steeper slopes. By the end of the book, readers know the difference between complex and simple machines and how inclined planes are used in everyday life to make lifting and lowering objects easier.