Cut the MDF

• 1). Measure the width and height of your existing mantle with the tape measure.
  
  
• 2). Measure two pieces of MDF 6-inches wide and match the height of the mantle. Cut the MDF to this size with the table saw. Measure and cut two pieces of MDF 4-inches wide.
  
  
• 3). Measure and cut two pieces of MDF 4-inches wide and the height of the mantle.
  
  
• 4). Measure and cut a piece of MDF 7-inches wide and the width of the mantle.
  
  
• 5). Measure and cut a 4-inch piece of MDF the width of the mantle.
  
  

Assemble the Surround

• 1). Apply wood glue to the back of the 4-inch pieces of MDF that are the height of the mantle. Place these on top of the 6-inch pieces to leave a 1-inch gap in on each side. Secure the pieces together with finish nails by driving one into each corner with the nail gun.
  
  
• 2). Apply a bead of wood glue to the top of the 6-inch wide pieces of MDF. Place the 7-inch piece of MDF on top of the 6-inch pieces. Secure the pieces together with finish nails using the nail gun.
  
  
• 3). Apply a bead of wood glue on each end of the 4-inch piece of MDF that is the width of the mantle. Set this piece under the 1-inch lip of the 7-inch piece. Secure the pieces of MDF with the finish nails.
  
  
• 4). Set the surround upright and place it in front of the fireplace.