What is included here are the files that you need to print to get the dual lock, which is the Idler Body, the Pulley Body, and the right Lock.
You need an extra M3x35 screw with a spring and an M3 square nut, that you should have gotten together with the original MMU3.
The rest of the files and instruction to build you get from the Ultimulti file collection. Just don't print the following parts:
I haven't built it myself yet, as I am traveling at the moment. But I will update with real pictures as soon as I can. Added pictures are just a 3D-model. Also the pictures depict the legs for the MMU3 Community Version, which I have released earlier. (Look for remixes in the Ultimulti and MMU3 Community Version.)
EDIT: I have refined the Idler Body somewhat. It is now in revision 1.11
The author remixed this model.
I took the idea from the Ultimulti with double lock for Coreboxx, but I did not like how the author “destroyed” the nice look of the original Ultimulti design, on both the Idler Body and the Pulley body. So I did a remix based on the original Ultimulti files, to add a second lock on the right side. I tried to add the nice angles that the Idler body has on top, to keep the design consequent. The right lock is just a mirror of the left lock, thus the text is also mirrored.