Once you're working on a higher-quality PCB and can achieve a trace thickness of 0.15 mm, you need to cover the copper portion of the PCB that isn't the active part with the copper. It's very easy to short circuit. That's why I decided to share my design: an easy, quick-to-print (less than 3 hours), two-part frame for catching and easily removing the screen print mesh. The hard base allows you to press the squeegees against the PCB to evenly distribute the soldermask. Good luck with your project!