The buildings and the hardware
The local building mix affects the hardware we see. In older single-family houses the doors often keep original, mortise-style locks or rim cylinders that need parts not carried by general hardware stores; those cylinders wear and require measured replacement. Mid-century apartment buildings tend to use threaded cylinder systems or sectional cores, which change how we rekey or replace locks. Storefronts and small commercial doors often have heavy-duty exit devices, metal jambs, or panic hardware needing different fasteners and sometimes reinforcement plates. Different door construction and edge prep mean the same brand of lock can fit very differently from one building to the next.
