The half inch long threaded sealed portion of each screw is what sticks out below the bottom of each rocker moulding hole and anchors into the rocker panel. I have heard back from a lot of the people that I have sold these to, telling me that they fit great. I have not had any complaints about these. If anything, the sealed portion, which can vary in thickness from screw to screw, is more often than not, a little wider than the rocker moulding hole, so when it is screwed in, fits very snug, although none of the sealed portion should be left inside the rocker moulding hole once the screw is secured into the rocker panel.
I have seen other original screws used to secure these rocker mouldings that do not have the shoulder on them, they are completely threaded. The ones I have seen are always shorter than the ones shown in the picture, for some reason. That would mean less threads from each screw attaching to the rocker panel.