The jig holds a standard 2 wire cable in place for easier soldering. I printed in PETG using a 0.4 nozzle and a 0.2 mm layer height on a MK4 with Matte Black Prusament.
I soldered SAC305 with the iron at 340 C with no problems (there is an air space under the COB for cooling).
The COB is quite a tight fit, so I used a file to remove any imperfections on the internal sides but it didn't take much.
It worked pretty well first time. I also used a pair of forceps to push down slightly on the insulation of the wire being soldered while it cooled to keep it in place.
The author marked this model as their own original creation.