John,
I think with security nowadays, even a 3mm nut would be detected in your carry out.
When I worked in the factory many years ago, there was no need to steal anything. You just took the bit you wanted to the foreman, and he would write it off and give you a bit of paper to give to and get you thru security.
You could buy slightly off colour body paint and matching primer undercoat at 1 squid a gallon, enough to do at least two cars. I bought an Everflex roof cover (vinyl top) that had been made slightly undersized. Purchased for 5 squid, then taken to the trim shop and they would cut it down for you and put the seams in the right places, ready to fit to your car. Then you would book a roof trim fitter from the factory for a Saturday or Sunday morning, to come to your house and fit it for you, 25 squid all in. He would even have the roofing underfelt and stainless trims with him, and dress and bend them to fit your car. 30 squid for a 1 grand roof, guaranteed to last at least 20 years (or so they said).
But also I have seen people praying for heavy rain. They would take a car battery, slung around their neck, and all covered over with their cycling cape, and cycle past main security. The security men were reluctant to come out of their hut and get wet.
Sadly those times have long gone. Nowadays, with JIT (just in time) operating thruout factories, there is very little unaccounted for, and negligible wastage.
Bogs
