Hi Les,
Not quite sure what you're referring to here. If you're talking about the height adjustor for the third wheel, I've seen some with the same adjustment screw and knob as the regular 4 wheel models, but also some with a large wing type screw. If you're talking about the screw for mounting the wheel assembly to the housing, it's just a regular machine screw with a couple washers and a hex nut. Same for the one that mounts the wheel to the yoke. Hope this helps,
Jeff
