A simple filament clip which prevents the filament from unwinding reliably!
I've tested many filament clips in the past, but couldn't find one that I was 100% satisfied with.
Out of this need I have designed this small clip!
This is the easiest way to attach the clip: Hold the end of the filament between your thumb and index finger, and press down on the previous winding with your middle finger. This way you can loosen the previous winding a bit to make it easier to get underneath with the clip to attach it. Do it a few times and it will be done in a few seconds.