Plain White Tee + A Pillow Case

I got this pillow case set from a thrift store a few months ago and never found anything to do with it, then I got a bunch of men's white shirts.  It was destiny.

You'll need:
a white t-shirt
two pillow cases (or any other fabric you like)
scissors
pins
and a sewing machine

Step 1: Preparing the Pillow Case

Rip all the seams and sew it into a long panel.  Make sure it'll fit the widest part of your thigh, if it won't do this then you'll need more fabric.  Sew all of the rough edges down.