Check out this door mat boot scraper from Home improvement expert Danny Lipford. Just watch the video tutorial to see how to make door mat boot scrapers on your exterior stairs.
Scrub brushes screwed to your steps are perfect for cleaning shoes and boots to keep from tracking dirt in the house. Scrub brushes with a plastic body won't rot and last longer than wooden brushes.
Start by drilling two 3/16" holes in each scrub brush. Attach the scrub brushes to the bottom step with 1 5/8" coated decking screws. Hose out the scraper periodically to remove dirt, and unscrew it when refinishing the steps.