Wherever the cut line was on the foot draw or put a line of tape on the other leg and measure there from that line to 1½ inches above the heel(You need to leave room for the elbow joint). (For example, If I had lost my right leg than I would take the line the surgeons cut on and draw it on my left leg and measure on my left leg.) This is one of your PVC measurements. Next, take your shoe of choice and measure from the heel of the shoe to the place where the shoes roof is just a smidgen over 1". You may have to trim down this piece a tiny bit.