"A foundational look at screws, explaining how these simple machines work and describing some common examples, such as jar lids, that have been used throughout history"--Provided by publisher.

Simple text and photos show how screws, nuts, and bolts are used in toys. Uses simple language and labeled photographs to explain the scientific principles behind their use.

All people have jobs to do. Some jobs take a lot of energy. Simple machines help people get jobs done without working too hard. There are six kinds of simple machines: inclined planes, levers, pulleys, wedges, screws, and wheels and axles.