One other solution is to "simply" add a lock, ignoring the details of the current doorknob.
The padlock is actually dubious or an actual code violation, and the lock you choose to add should be releasable from inside the closet (which is why that's probably a code violation - locking people in closets is not safe.) It may be a "not uncommon&...
I can't tell what the existing backset (distance from front-side edge of door to center of knob shaft) is, but you can buy mortise locksets that lock. A bit of chisel work would expand the existing mortise.
I shudder to offer this link, but as an example of widely available things, mortise lockset
The linked one appears to have a 2-1/2" backset.
WD-40 is not a lubricant which is why it's only lasting a short time.
Use something to clean it out, carb and choke cleaner is reasonable and follow that with some compressed air.
Then apply some graphite-based lock lube to the moving parts. These are also often called "dry" lube and they don't hold dust like oil-based lubes can.
Once it all moves ...
That type of latch rotates (there is a half-cam inside)
That square hole you see is engaged by the shaft on the missing knob, and rotates that piece.
You can use anything to turn that either way. A screwdriver with a bit too big to fit straight, but will fit in 'diagonally' will do the trick...
a quarter turn should open it fully.
This is provided it is the ...
If you have the doorknob - look at the back of it and see how it actuates.
I'd suspect theres a vertical bar that rotates, and pushes on the top or bottom black bit, making it move to the right in the photo.
You can probably duplicate that action with a screwdriver, put the tip where the letter A is, and push the tip to the right.
I looked into this as it was something that I had not heard of before.
I did find a US site that sold such handles but their latch mechanism is quite a bit larger than the typical door latch. Marchello and Rome
A second option would be to buy a European latch and fit it to the door. Link
The Backset is slightly different (57mm = 2 1/4" versus a ...
If you're certain the wall is not supporting any load other than itself, you could over cut the opening and fasten in a wood jamb, with double 2x header (bear the header on the vertical jambs). Although a non load-bearing wall would likely be fine without a header, it's still supporting its own weight and you will want something to fast your door to.
How do ...
Understand the constraints of the existing framing. I'd have probably kept the new vertical 2x4 you added 3.5" shorter (along with the plywood spacer you added), and made the header stick out 3.5" on that side to rest on top of that new 2x4. You'd essentially be using the existing vertical 2x4 as the king stud and your new 2x4 as the jack stud, ...
This looks like the sort of latch which is activated by pressing the end of the piston-like piece towards the strike plate. If it's not sticking this can be done with your fingers, otherwise MacGyver some sort of prying scheme.
When closing the door -- turn the knob to retract the latch tongue, pull the door quietly shut and hold it there, then turn the knob back to quietly let the latch tongue into the strike plate.
With a little practice you can do this absolutely silently.
When your children are older they will learn to do this when they want to sneak out.
Sliding a cake knife, piece of plastic (credit card or similar) down at a 45 or 60 degree angle in the gap where the strike plate is, start above, while pushing gently on the door is usually enough to slide the plunger back and allow the door to open.
You might try grease instead of oil if looking for quiet (petroleum jelly is a relatively "clean" or "clear" grease that's found in most houses) and perhaps pack the strike plate hole with a hard grade of felt - either a bit to quiet operation while still latching, or completely to not latch.
Here is a cheap idea you can try now.
Turn handle so metal part is withdrawn completely into door.
Put a quarter over it.
Tape quarter into place with duct tape. The quarter is because with just duct tape the metal protrusion piece will cut thru the tape pretty quick.
Now the door does not latch. You no longer use the latch. You can push it open and ...
That looks like an excellent candidate for a pocket door. Since that is a meeting point for a few openings, hiding a door is going to look much cleaner, save space, and allow you to open and close with clearance.
An economic door that I have used that would fit this opening is - https://www.homedepot.com/p/Johnson-Hardware-1500-Series-48-in-x-96-in-Pocket-...
Here's a picture of an antique doorknob assembly. As @PhilippNagel commented, these should screw off once you remove the setscrew. If it's not unscrewing, double-check the other doorknob and remove a setscrew from that one, then hold both knobs and unscrew. One of them should come off.
When the remote stops working but the opener still works from the wall switch and/or keypad, it's the transceiver in the opener that has gone bad. It's either part of the main control board or if separate, probably the most expensive board in the opener from what I've found.
For far less money, I bought a web switch that connects to my home wifi and mounted ...