I simply bought two five tread pressure treated stair stringers and had them(home depot)cut a 2x12x16' PT into 5 36" pieces and using 3" deck screws put them together

then I added a 2x4 on its side under the first tread

and it sits perfectly on the top tread of my fiver's steps,shoot two 1-1/2" screws up through the holes in the fiver's top tread into the 2x4 and the stairs will sit nicely.Since I have two permanent sites in Ontario and Florida I built two and left them at each place however it takes minutes to assemble/disassemble and they stack nicel;y behind the hitch across the truck bed,i hope this helps.
Red Green:
So remember,If women don't find you handsome,
they can sure find you handy.