Back in those days, the only kind of sneakers girs wore were Keds-like sneakers.
I developed the next method to take advantage of the one night a week my parents were out of the house. My sister took advantage by going out with her friends. I took advantage by using her sneakers. I prepared my masturbation material (Sears catalogue, Junior Miss Clothing :-). I put one pair my sister's sneakers on the floor parallel to my body soles up with the toes pointing towards my head. I took a second pair of sneakers, and put one parallel to my body between my body and the pair already on the floor as a 'spacer' so my penis would rest on the soles of the first pair. I arranged my body and the sneakers so my penis made contact with the rubber on the soles corresponding to where the balls of the feet would be.
The remaining sneaker was placed over the heels of the other sneakers perpendicular to the other three so it is standing up on edge. I put my leg over this one. This sneaker kept my leg from coming down and pushing the penis flat into the other sneakers. I called this sneaker 'the elevator' and it gave me a little more room to maneuver my penis over the rubber.
My hands were free using this method, so I could page through the catalogues.