The buildings and the hardware
The built environment affects the hardware we see. Older doors often have mortise locks, heavy wood frames, and surface-mounted hardware; those require different machines and longer teardown than modern bored locks with 2-3/8 inch backsets. Where there are newer homes or renovated entries we encounter bored cylindrical deadbolts, light-gauge metal storm doors, and latch mechanisms made of stamped steel that wear faster. Small commercial storefronts use rim cylinders, panic bars, and sometimes multi-point electro-mechanical hardware. Knowing the door construction tells us what parts and mounting hardware will fit and how invasive the work will be.