I just bought a house from the 1920s and all the interior doors are mortise locks with skeleton keys. I would like to change some from key to privacy with a thumbturn. Is there a way to simply convert or do I have to replace the mortise lock to a privacy lock first? My doors do not have backplates/trim plates and the wife doesn't want to add them to the door, but through my research it doesn't look like I can just buy a thumbturn and insert it. Just want to make sure I'm not missing other options. TIA!

2 Answers 2


I've done that for a bathroom recently. I replaced the locks of several doors entirely with this lock (fit like a charm). For the thumbturn, I purchased this plate and thumbturn kit. It required a bit of 'macgyvering' but it turned out well.

I had to combine the thumbturn provided in that kit with the key provided by the lock. The thumbturn provides a handle, a square 'arm' with a hole in it, and a pin which connects the thumbturn and the 'arm'. Luckily the shaft of the key fits in the hole of the thumbturn; by cutting off the handle of the key (to appropriate length) and drilling a hole in the shaft you essentially swap the 'arm' provided with a functioning key. Photo illustrates the result: photo of 'macgyvered' key-thumbturn result

The pin portion of this thumbturn contraption is hidden behind the plate provided with the thumb turn. Result works and looks great.

enter image description here

  • i guess macgyvering it is! we dont have the backplates at all so I'll have to see what I can find. How did you attach the key portion to the thumbturn? last thing I need is my DIY to break. thanks
    – JTC
    Apr 7, 2017 at 14:35
  • @JTC The thumbturn has a hole drilled through it and comes with a pin. I drilled a hole in the key of equal diameter and stuck the pin through. There is more detail about this in the post. Apr 7, 2017 at 21:06
  • 1
    I don't have enough reputation to comment on the above answer. It seems like a great solution, but it would make it impossible to unlock the door from the outside. For example, if a child locked themselves in the room, there would be no way to unlock it from the outside, even if you had a key.
    – TCK
    Dec 28, 2017 at 20:41
  • @TCK true, this is a risk. Dec 29, 2017 at 14:35

You can insert a thumbturn if you see a lock below or above the door latch (when viewing the edge of the door). In this case it would be a matter of drilling a hole to insert the thumbturn through the locking hole inside the door. My advice would be to remove the mortise lock assembly from the door so you can test the locking device before doing anything else.

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