@christofferra_319142 Thanks, now I got it :-)
@AlexP I'm glad you liked it! :) Thank you for posting a make!
The "holder_nut" is to keep the holder from collapsing if there is no phone mounted. Otherwise the bolt will just fall through the upper leg. But when a phone or something else is in place it serves no function. (edited)
I printed it in PLA+ and it prints and works fine.
I use it in my diy encloser for the MK4.
I did not understand what the holder_nut is needed for. So I left it out...
Thanks for the nice print :-)