Back in days of yore, I worked at a defense contractor in the facilities department as a draftsman. I created pencil drawings of office space plans, hvac, electrical, misc building repairs.
One day an executive was worried that a new crane rail system might not be high enough. So my boss wanted me to draw an elevation view of the ground line, the crane and all the stuff that was being lifted, to show that it would clear the base stuff.
The stuff in question was a base stand, the base of the nose cone section of a Peacekeeper missile, the re-entry vehicles sitting on the base, and being lifted over that, the nose cone shell and above that the crane rail.
But in order to draw it all, I needed to measure it. All the parts were in a top secret room in the manufacturing building. I had to get special permission, then when I showed up, they stopped me until they checked out my story. Then they watched me like a hawk while I was measuring.
I wasnt allowed to actually touch anything. So I was standing about 6 feet away from the conical, carbon fiber re-entry vehicles, which is the casing for the nuclear bomb.
I eventually got access to every top secret room there.