How do you make a box header?
Moreover, how do you make a 2x6 header? Header in 2x6 framing. Use three 2x10's and two 1/2 inch pieces of plywood or OSB. This will make 5 1/2 inches thick, which is the width of a 2x6. Start with a 2x6, then plywood, then another 2x6, then plywood, then the last 2x6.