I spent most of my 20s doing all kinds of things, from installing security cameras, to running cable, to on-site IT work - a lot of it in and around law enforce

I spent most of my 20s doing all kinds of things, from installing security cameras, to running cable, to on-site IT work - a lot of it in and around law enforcement (jails, police stations) - and I was often amazed at the kind of access you could get in some places just by showing up with some crimpers and a box of cat5 and telling the person up front that you're here for [whatever]. Like you said, in many situations if you just act like you know what you're doing no one will question you.