Thanks for posting the hydrant head photos, Magdalene!
Aha.....the picture that is worth a thousand words :-) ....... the little set screw was out of view in the original photo so now it makes sense. If that set screw was loosened, the plunger rod that goes down through the pipe would just sit there, not moving, while the handle went up or down and no
water would come out. The set screw grabs the plunger rod when tightened and allows the handle to move that plunger rod up and down to open and close the valve at the bottom of the pipe. Where the one design uses adjusting nuts to find that 'happy place' where the water flows well with the handle up and the water stays shut off with the handle down, the set screw model like what you guys have employs loosening the set screw if you need to re-adjust where along the top of the plunger rod you want that screw to grab.....finding the happy place by loosening, slightly moving the handle, and then re-tightening the set screw to see if the happy place has been reached. I can see on major, MAJOR advantage to the set screw design: No disassembly of the flat steel arms that attach to the handle and pull the rod up to access water. With the adjustment nut design, you have to take the handle and the steel arms off each time (!!!) just to turn one of the adjusting nuts a quarter or half turn, then reassemble to see if happy place has been achieved. Not fun on a nice day, really irritating in cold weather. Are you guys okay with posting the brand or source for that hydrant? Again, much thanks for that extra photo.....cleared up the confusion immediately!