My Moen shower head has the main head and also a magnetic mount wand. There is a little handle that diverts  the water from the main shower head to the wand. It turns about 120 degrees back and forth to change the flow. The ribs act as a stop to restrict the turn to 120 degrees and make it easy to switch to the flow 100%. The top of the ribs broke so the handle just spun all the way around. Made this replacement.

I made a prototype in petg. It seemed to work ok but was never tested long. I made the final model in polycarbonate. I used 100% infill.

I know this is unlikely to be useful to anyone else but figured i'd share just in case.