The Christner Heavy Duty Pocket Door Frame utilizes four tubular steel posts that are precut and ready to snap into the top and bottom brackets for a quick and easy installation. These tubular steel posts are strong and straight giving your door an ample pocket to slide into. The 3/4" furring strip is assembled in our shop. For the 3 1/2" wall, we use a 3/4" x 1 1/2" 16 gauge tubular steel; and for a 5 1/2" or thicker wall width, we use 1 1/2" x 1 1/2" 16 gauge tubular steel. Unique to Christner's design, the top and bottom brackets make this system very versitle, allowing you to expand the width of your wall when necessary.