If you use chafing gear that is not fast to the line you are protecting, you never know if you are protecting the line, or the thing that is chafing the line. For light loads, it will do what you want. With heavy loads, you will be surprised!
A fellow disputed that with me once, when we were rigging hurricane moorings. He was using fire hose that was a pretty tight fit to the line he was protecting. After the hurricane, we checked, and sure enough, he had tiny burn marks underneath the chafing gear.
I always make chafing gear in the traditional way, by wrapping cloth or leather around the line, and covering it with small stuff using chafing gear hitches (same as a blanket stitch). That way, the chafing gear is fast to the line it protects.