As a kid I was an avid reader of Heinlein and Asimov, and they were always talking about slide rules (Astrogators navigated space with them!) This was the late

As a kid I was an avid reader of Heinlein and Asimov, and they were always talking about slide rules (Astrogators navigated space with them!) This was the late 80s, and I couldn't find one. So, I found plans for one in the public library and built one. Later a math teacher gave me his. Playing with slide rules would be useful. Building a slide rule would be even more useful.