This plan may be used or adapted for most any size double axle flatbed trailer and includes steps for the optional spare tire carrier, electric brakes and stake pockets.  Plan is easily adapted for various sizes of flatbed trailers.  Trailer pictured is an 8' X 16".

Sample paragraph

Step 2.  To lengthen the sides to 22', support & clamp the 24"  pieces to the front of each side with the 45% mitered end forward (after you bevel the edges of both pieces where they join for a deeper weld penetration). Clamp a piece of angle over the joint to keep the two pieces straight and a 3" x 5" x 3/16" flat bar on the inside for a gusset. Weld the joint & gusset. Add the front 82" frame piece to enclose the front end and weld the corners as you did the rear.