Beauty, Efficiency and Value all backed by over 15 years of experience & premier Andersen® Certified Installation, Service and Warranty. As a premier St. Louis patio door company, Keller Window & Door is your best choice. Choose from our huge selection of Andersen® patio doors and windows. Find the perfect style and function that’s right for you at lower costs than other providers while still getting that same Andersen® quality, durability and Certified Andersen® Installation and warranty you can trust. Whether it be a simple replacement door, windows, or complex design, Keller opens the door to endless possibilities. Keller offers a one-stop, start-to-finish service for your window replacement project? At up to 40% less than other leading competitors, Keller Window & Door offers you an easy and reliable complete replacement process, all in one place.