OK, I'm embarrassed to ask for some help. I put an "XTS E-Z ambidextrous sling adapter" over the castle nut of my AR. All is put together, but I can't seem to tighten the adapter (cinch it down) over the castle nut. It just swivels back and forth on the buffer tube. The box has a picture of an allen wrench on it, so I tried finding one that would tighten it where the removable swivel attachment point goes in, but can't seem to figure out what should be something very easy to do. Anybody put one on with advice? Thanks.