We ordered this shoe cleaner to keep outside the back door, on concrete.  By itself, this is worthless on concrete as there is no way to hold it while cleaning your shoes.  Also, it rusted quickly on the bottom where the concrete scratched the paint.  I ordered the steel base and now it works good.  The side brushes do a good job, and the bottom has the metal edge that you can scrap off the mud as well as the little brushes.  For deep tread on your work boots, you will still need to scrap out the grooves, but on smoother soles, it cleans good.  You will definately either need to screw it to a wooden deck or buy the base to use it on concrete.