This is a printable version of a well-advertised psoas release tool. I printed this with 20% infill in PLA. Due to the printed layers it's not as smooth as the commercial molded version. If you have dry skin consider using this while wearing a shirt or put a cloth between it and you so it slides more easily. I'm sure you could sand the layers down as well. I am not a doctor / therapist - use at your own risk etc. etc. There are lots of youtube videos on how to use these. 

The corners are chopped off to fit diagonally on the X1C size bed. Too big for A1 Mini - soz. 

There are six recesses for 0.5" diameter adhesive rubber bumpers if you want to use them. Designed to print without supports. 

Onshape link if you'd like to modify any of the dimensions. STEP file in the downloads as well.