I bought these but when i try to shorten the length, it slips right back to full length. Doesn't seem to be enough friction to lock it. Why?

I am the one that asked the question (couldn't edit it later). I figured it out. I was using it incorrectly. the adjustment seems to stay where you put it once you loop the bungee over the ball and it "pins" itself in place. thank you Lowes for trying to help with the reply.

Perhaps you are pulling the wrong end, the end that goes straight through does not have any resistance and will return to full length.