The RockShox Judy is missing threads to attach a mudguard. This Adaptor fits into the struts of the fork bridge and is secured using zip ties (max. 7mm width).
It uses a standard M6 bolt with 10mm hex-head and a nut (preferably nylock).
If you care about your paint you should put some transparent tape under the zip ties to prevent scratches.
Print in a UV-resistant material like PETG or ASA. PLA or ABS likely won't last long.
The author marked this model as their own original creation.