A guy would just do a walk around with a baseball bat and hit parts to see if they fell off. If they did, it was time to replace them. If they didn't, the aircraft was good for another 1000 hours until the next maintenance window.
Also, fairly major maintenance taking place (replacing tires, etc.) on active runways at major US airbases, with USAF Security Forces with M4s at low ready pointed at us. I was the only person on the plane with the authority to actually be there more than in-contact-with-plane.
The low level guys guarding planes probably didn't have the autonomy to put their weapons away while guarding. This is SOP for a lot of military activities. Your weapon is out and held at the ready. Any other position invites liability as you can't get up to aim quickly enough in a firefight.
