Adding collection to Collection Template Page not limiting to current item

I am trying to show all documents related to a product, but the CMS Collection Pages - Products Template is showing all documents, not just those related to the current product. I have a blog example that I cloned and it works in that it only shows categories related to the specific blog post. I feel like i’m missing something very basic.

I have two collections:

  1. Documents
  2. Products, where I have a documents field that is multi-reference pointing to Documents


OK, slow learner. I bound the Collection to the actual collection, rather than the multi-reference field. I had to scroll up in the picker to see it. Doh!