I created this thing after seeing a couple of other keychain things that did not fit my needs. I wanted something that could hold more keys and makes it easier to access single keys. The S shape allowed for a compact design and easy access to the keys.
You can use M3 or M4 screws for the two main screws and a M3 or M2.5 for the middle one, in the photo you can see M3 and M2.5 beeing used. Make sure to either use self securing nuts or locktite.
Instead of a key you can add the Ring thing to be able to fasten something to the keychain. Keychain 09 is a slightly smaller version where the ends of the S are shorter and the parts are over all slimmer. Keychain 10 is like 09 but a bit thicker..