What do jar tops and water-bottle lids have in common? Both of them are screws! Screws are simple machines. They help us to do jobs more easily. But don't take our word for it. Put screws to the test with the fun experiments you'll find in this book. As part of the Searchlight Books™ collection, this series sheds light on a key science question - how do simple machines work? Hands-on experiments will help you find the answer!