Mark could you post a picture or diagram.
Sorry it took so long to get back to you.
I made these from a scrap block of steel by drilling the hole, sawing in half, and filing the "V"s. Took me about 15 minutes to make.
Here is a ferrule clamped using these blocks in a vise. I like the brass ferrules because there are no sharp edges or protrusions to snag you or anything else.
You can buy a tool like this commercially ( but it is so easy to make, I can't imagine why anyone would ). The commercial ones have a 1/4" rod bent in a "U" shape for a handle and a block mounted on each end. The advantage to doing this is it is easier to keep everything aligned and you can also use it with a hammer instead of a vise.