PARAMETRIC Assistive Handle for a better grip on knobs

Here's the story : Sometimes you want to have a shower and wash your hair, sometimes you don't need to wash your hair. So you unscrew a knob that lets you adjust the height of the shower head, that's if you can grip it, some can no more, that's what this design is about : Helping people gripping knobs.

Enjoy, and keep 3D printing useful by helping someone with this.