Make 6 short 2x8 pieces for both ends of each beam, each 11 3/8" in length. Cut these from 8' 2x8s.

You will make 24 of these pieces total.

Also make 4 end caps, one for each end of both beams. You can make this from the left-over sheet material from the door or window modules (5/8" plywood).

The plywood endcaps measure 7 1/2" by 12"