The second picture (holding up the hover board) is the oldest set (roughtly 17 years ).
The third picture shows a 5 or 6 year old set holding up some I-beams.
I have to paint both sides of 25 sheets of plywood so I needed 6 sets (12 horses) to make the job flow more easily.
Step 1: Thoughts to ponder before you begin
Stack-ability - Each saw horse is 1/2" longer than the one beneath it. Hence the numbers! If the braces were about 2” wider, the horses would stack against the braces rather than the legs. The first set I built was like that and it was pretty cool. Make adjustments as you see fit.
Materials - The best lumber to use would be KD (kiln dried). Generally your other choice is GDF (Green Doug Fir) or equivalent. KD lumber will not warp (very much) while GDF will, as it dries, turn into interesting potato chip (or pretzel or your other favorite curvy snack food) shapes. Unfortunately the longest KD 2x6 I could find was 8’ which would not have been efficient for this job.
Fasteners - I used drywall screws. If you will be using these saw horses for their name sake's purpose (holding up lumber while you saw it) please be advised that drywall screws are hardened steel and carbide tipped blades do not like drywall screws. If you think there is a possibility of hitting a screw with a blade, using general purpose wood screws is a better choice.