I would like to order a new cylinder for my door and need to provide measurements. I do not know which of the measurements on the right (20 or 30 mm) I should choose:

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Specifically I do not know whether the silver ring is something which is fixed to the door (more precisely - to the white metal box in the last picture below), or is it something I will be able to remove when removing the current cylinder?

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This looks like a Euro Cylinder Lock. You can find resources on the Internet explaining how to measure and replace them.

The silver ring is an escutcheon. It is a trim piece that covers the rough hole in the door where the cylinder goes through. It is likely to be fixed to the white part of the door. You might be able to remove it when the cylinder is out, but it is probably best left in place.

Therefore the measurement for the right side is 30 mm. I can't see what is happening on the left side so I won't comment on that. You can check the measurements more easily by temporarily removing the cylinder.

Try to get a cylinder size that protrudes as little as possible and also includes anti snap features.

  • Thank you - this is very informative. If by "It is likely to be fixed to the white part of the door" you mean that it is screwed to the white part and not for instance soldered to it, then I will indeed temporarily remove the cylinder and see how it was fixed. I would prefer to remove it because the cylinder is going to be an electronic one which has a "thing you use to turn it" on the inner dise (the right side on my picture. As for the left side, it is measured to the edge of the door, the dark part is just a metal piece which does not interfere with the lock.
    – WoJ
    Dec 3 '19 at 22:49
  • 2
    Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, props for taking our tour before posting; few newbies do. Dec 3 '19 at 23:22
  • I'd be surprised if it was welded on. Could be a friction fit, maybe look for a notch underneath to carefully lever it off. Could be fastened with a grub screw into the side or even screwed securely from behind. However if it does come off then you might still be left with a protruding fixing underneath rather than a flush face.
    – James
    Dec 4 '19 at 0:03
  • I will check tonight by removing the cylinder (I will have to learn how to do that anyway) and will be back with what I found out.
    – WoJ
    Dec 4 '19 at 12:07
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    After removing the cylinder I saw that it is fixed to the lock. I may be able to remove it but there are elements, as you suspected, which stick out. So I will leave it as it. Thanks for your answer!
    – WoJ
    Dec 5 '19 at 20:31

That ring is part of the lock. A door is (typically) a big rectangle of wood or metal with some holes drilled into it to accommodate latching & locking mechanisms.

The most important thing is to make sure that the new lock will fill the existing holes and be designed for the right distance not just from the edge for the bolt (20mm) but also on the big flat side of the door from the edge to the existing metal ring. You can often make holes bigger, but you can't easily make them smaller (or at least not smaller and secure).

  • Thank you. I added one picture as I was not sure what you meant by "lock". Is the ring part of (=irremediably fixed to) the white metal box with the locking mechanism (which itself is fixed to the door), or does "lock" mean the cylinder, which I will remove (and then remove the ring as well)? I think you meant the former but I wanted to make sure. in other words, I have to choose 30 mm in my dimensions? As for the shape, this is a standard shape in Europe.
    – WoJ
    Dec 3 '19 at 21:04
  • I also realized that I was not clear enough: I will be changing the cylinder only. I will clarify that in the question.
    – WoJ
    Dec 3 '19 at 21:06

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