My wife called me at work and informed me that the door was not working.

Well, I've been doing doorknob repairs for a long time in my student lodgings, and I was confident that I could fix them normally.

However,

"The lever handle moves, but the latch bolt does not release"

I've never seen such a phenomenon.

I removed the lever handle part and looked at it, but I couldn't figure out why.

I did not observe any anomalies in the latch part, either.

However, I found an unfamiliar piece of metal sticking out of the latch area. While holding the piece of metal with pliers, I turned the movable part of the lever handle, and the latch bolt happened to move.

I opened the door, without missing its timing.

Then I dismantled the doorknob at once.

-----

Observations showed that the transmission part of the latch had been damaged by metal fatigue and could not be opened or closed at all.

I ended up with a deadlocked situation, where I couldn't open or close the door and, therefore, couldn't even disassemble the doorknob.

If such a condition occurs in a closed room, such as a toilet, there is no way to escape.

So, I decided to destroy part of the door in advance to ensure a way out.

So today, I made this video as a note for myself.