I've seen on Toyotas and also at Universal Studios bolts on rides are marked with paint presumably to indicate that the nut hasn't backed out. Are airliners marked in this way? Is checking the bolts simply a visual inspection, or do the inspectors need to get out a torque wrench?
Yes aircraft fasteners are often torque marked, and almost all safety critical fasteners have an additional preload locking mechanism. Often these fasteners use mechanical locking features such as cotter pins, safety wire, or safety
cable.