Apply glue to one side of two 1x3 leg pieces and place on headboard legs as shown in illustration. Nail every six to eight inches using 2-inch nails, making sure to keep top and outside edges flush.
Trim the headboard tops and bottoms by applying glue to 1x4 panel trim boards and nailing panel trim boards to the tops and bottoms of both sides of headboard. Use 1-1/4 inch nails and keep outside edges flush.
With headboard facedown (the front of the headboard will have minimal nails showing), apply glue then nail remaining two leg pieces to the sides of legs. Keep the front edge flush, but the back may have a slight overhang. Use 2-inch nails every 6-8 inches.
Apply glue to the top of the headboard. Line top trim piece up with outer leg piece and nail down, nailing every six to eight inches. Keep front and outside edges flush.