Step 1
Remove all bedding such as sheets, comforters and pillows from the bed and set them aside, out of the way.
Step 2
Remove the mattress and the box frame from the bed with the assistance of another person and set them out of the way as well.
Step 3
Look into the bottom of the bed frame to determine whether there are wooden bed slats already in place. If so, you can measure them to determine their width. If no slats exist, you will measure the bed frame.
Step 4
Place a tape measure at the leftmost side of the bed slat, or at the left most side of the bed frame rail. Hold the tape measure flush with the interior side of the vertical rail and stretch it across to the other side of the bed, stopping on the interior of the right vertical rail. Ask the other person to pull the tape measure all the way flush to the right side of the rail and note the measurement. The measurement is the total board length that you need for each bed slat.