Historic American Engineering Record study on trusses.
Download here (originally from the National Park Service). If that link doesn’t work, try copying and pasting this link: http://www.nps.gov/hdp/samples/HAER/truss%20poster.pdf
I love this poster. I think I should print it in large format and hang it over my desk at work. Does anyone know if the NPS still distributes these in hard copy?
Preservation in Pink 