bkeske,
It snaps in place and stays there firm. It may be my big fingers, clumsiness, something else, but it does need some aiming when placing on, and finding the little protrusion to pull when taking off. Video shows the principle. However, there is no headshell in the video so everything is more accessible. In my experience, the part to pull to "unlock" when taking off is very close to wires. It is small, too. Fingers have to fit between the plinth and cartridge, avoid wires, locate the protrusion, and pull it in the right direction while keeping the arm in one place.
Compared with Soundsmith’s approach, Ortofon’s OM series protectors are like a breeze. They do not lock, but I have never had one fall off. Maybe by luck, but possibly by design, too. The shape of the front of the cartridge (stylus area) seems to have similar shape.
Again, it may be just me, and even for me the complaint is not major, but I have had Technics, Ortofon (multiple shapes), Audio-Technica and Soundsmith’s approach is not to my liking. I am a bit sorry I brought it up because it is really a minor issue on what I consider a decent (for me) cartridge that I would buy again.
EDIT: I just tried to put a stylus cover back on and off. To practice, I guess. Usually I do that when everything is off, but this time turntable was connected and amplifier set to phono input. I tried carefully and heard the noise. Basically, the protector rubbed against the stylus while being placed on. It did not seem to touch it when it was on, but pulling it over makes it go under a small angle at first and that is the moment it rubs on the stylus.
I doubt it makes any damage, at least not any more than the record surface would, but imperfect of a system it seems to be.