Plywood

• 1). Measure your mattress using your measuring tape.
  
  
• 2). Cut your plywood to match the size of the mattress using the circular saw.
  
  
• 3). Lift your mattress up, so you expose the box springs.
  
  
• 4). Slide the 1/2-inch plywood panel beneath your mattress and box springs on one side of the bed.
  
  
• 5). Lower your mattress, ensuring the mattress covers the plywood and that no edges protrude.
  
  
• 6). "Test" the 1/2-inch plywood by lying on the bed to see if it offers enough support. Decide if the bed feels firmer.
  
  
• 7). Apply a layer of 2-inch memory foam on the top of the mattress to compensate for any "hardness" you might feel as a result of the plywood.
  
  

Bed Board

• 1). Lift the mattress.
  
  
• 2). Slide the bed board beneath the mattress, ensuring the edge of the board remains flush with the edge of the box springs.
  
  
• 3). Lower the mattress, making sure none of the board's edges protrude.