A history and explanation of the basic lock and key combination that is the major technical foundation of property security, from the first Egyptian wooden lock to today's time lock.---from the publisher
32 pages 978-0690040586 Ages 5-8
Keywords: locks, keys, history, how things work, informational picture book, part of a series, 5 year old, 6 year old, 7 year old, 8 year old
