A few resources I came across looking for "the perfect fastener" for a recent product. None of these places are bolt suppliers - but one search lead to another on google, and here we are with some useful terminology and information.
Nuts & Bolts Pdf talks about how bolts work, forces, and specifications, as well as nuts and washers and locking compounds. Not geared towards theatre, or even construction, but towards racecar drivers, but still worth a read.
Glossary of Nut & Bolt Terms As titled - check here if you ever come across a fastener that you are unfamiliar with.
Nut & Bolt Identifier Tool is something I need for my shop at home (we have similar tools in my shop at work). I like how this encorporated both the bolt and nut identifiers.