Aqara U200 smart lock modification part for APECS thumb knob cylinder

Note: It was brought to my attention that covering up the thumb knob as shown here can be problematic because when the lock's snap protection has been triggered by a burglary attempt, access to the little button on the knob is required to unlock the door from the inside, so covering it up may not be a good idea for safety reasons. You'll have to decide if you're OK with that.

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This part lets you use an Aqara U200 smart lock with an APECS Euro cylinder that has a non-removable thumb knob on the inside end. This is not needed if your cylinder has a key hole on the inside end, instead of a thumb knob, or if the thumb knob is removable. In that situation, the U200 works out of the box without modifications.

You'll have to disassemble the APECS lock in order to be able to slide it through the opening in the Aqara mounting plate. That disassembly is not trivial.

This was printed with PETG, split into two parts (front/back) so it can be printed cleanly without supports. The two parts are held together by four 2-56 thread machine screws and matching 2-56 square nuts. 

Designed in Fusion 360, the model is available here: https://a360.co/4diJKUg

I previously created the same kind of replacement part for a Nuki smart lock, but I do not recommend that lock. The Aqara is better in every way. The older model is here: https://www.printables.com/model/263585-nuki-smart-lock-modification-part-for-apecs-thumb-