The buildings and the hardware
A lot of Somerton doors are older wood or metal frames with mortise or surface-mounted hardware, and that changes the work. Older apartment and house doors often have thicker, heavier strike plates and mortise locks that require precise fitting; in contrast, newer replacements use light-gauge bored locks and composite door edges that need different latch sizes and longer screws for secure attachment. Where buildings were updated piecemeal, you find a mix: stamped cylindrical locks on some doors, full mortise with cast brass on others. Matching trim and ensuring the latch engages cleanly are common parts of the job.