At home we have a shower which has two knobs, one for the temperature and another for the water flow. Both knobs have a button which has to be pressed to fully turn the knob, with the temperature knob this is kinda obvious because you don't accidentally want to twist the knob to the highest temperature, but I always want the water flow to be on the highest setting so I was annoyed by the button I have to press every time I twist the knob, so I made a ring which holds down the button.
This ring is for an elliptical knob with a width of 40mm and a height of 45mm