Inside a uPVC door mechanism https://www.helplocks.com - YouTube
Doorknob in my 1907 house stopped working, so I took the mechanism apart to fix it—this is what a 113 year old door latch looks like inside. : r/interestingasfuck
How to Lubricate a Door Lock - dummies
How to Reverse Handing on Interior Door Mortise Lock (with skeleton key) - YouTube
how a door lock mechanism works - YouTube
Inside the Actuator - How Power Door Locks Work | HowStuffWorks