Rubs face the direction the buck came from — that's why a clean line of rubs walking through timber points to bedding behind you and food ahead. Tree size correlates loosely with buck size. A rub on a 5-inch sapling could be any age class; a rub on an 8-inch hardwood with the bark stripped to 4 feet up is a mature buck.
Lines tend to track the same draws and benches year over year. A line you find in late October was probably laid down by the same buck or a successor who used the same travel pattern. Pair rub-line evidence with scrape locations and your state's rut date pages to time the sit.