Again, you may need to make only one if you have a smaller frame.
To do this, place your board flush at one end, near the corner of the frame and mark where your next cut will be at the other end.
NOTE: If you were to measure this mid brace where you will be placing it (two feet in on each side), then you are apt to get a faulty measurement, because we have not squared the frame yet, and the area might be bowed out.
