Measure the distance from one side of the bed frame to the other using a tape measure.
Take another measurement a foot higher, and then another a foot lower ensures that there are no variations in widths, as you move up or down the frame.
Purchase boards from a lumberyard measuring 1-by4-inch. The type of wood you use depends on how hard you want it. Oak is a strong, sturdy wood, but fir or pine work just as well. Cut each board roughly one-half inch shorter than the width measurements. A twin or full-size bed uses three or four slats, while a queen or king is best suited with five or six.
Sanding the edges of the slats with fine-grit sandpaper smoothes the wood out and prevents splinters.
Place one slat at the frame’s top close to the headboard, and then space the slats equal distances apart until you reach the bottom. A twin or double-size bed measures 75 inches long, so place them approximately 25 inches apart. A queen- or king-size bed is 80 inches long, so if using six slats space them about 15 inches apart.