It's not much of a design. Just as simple and sturdy a sawhorse that I could come up with. The emphasis is on light, sturdy, and stackable. Disassemble-able would be nice too, but that would compromise the other aspects, especially sturdiness. If you want it to fold or come apart, I'd recommend buying some of the better metal sawhorse brackets.
I previously built some sawhorses with a radial arm saw (or a miter saw), but this time I'll show how to make one with just a circular saw.
Materials needed for two sawhorses
I had some old painted 2x4s from a picnic table (which, ironically, was my temporary workbench when I previously built sawhorses). A circular saw will cut most of the way through a 2x3, but it's one inch shy of cutting through a 2x4.
So I flipped the 2x4s over to finish the cut from the other side. This time, I'm using some extra 2x4's to support the saw, though I could have just cut it in the other direction and not needed that. It's tricky to get the two cuts to line up, and I had to go over two of the cuts a second time.
If you are using 2x3s instead of 2x4s for the legs, you won't need to do this.
Here I'm cutting the 18 degree (18 degrees from square) bevel in the ends of the legs. It's best if the bevel doesn't go all the way across. That way, there's less risk of splitting the ends of the legs if the sawhorses are on uneven floors.
After that, I cut more slots, knock those out, then clear out more. If you clear out the whole dado at once, there isn't enough support left for the saw, so you wouldn't be able to use it to flatten the bottom of the dado.
Nailing on the legs. A bit of glue doesn't hurt. The more accurate the joints, the better the glue will work. Construction adhesive works better for larger gaps. Though, realistically, the sawhorse will be strong enough without glue.
I'm using some extra 2x4s to support the leg as I nail it.
I cut a stack of four of these at once with a circular saw. I used a clamp to hold the small workpiece. Holding a something that small by hand while cutting it would not be safe.
I thought I'd take it up a notch by dropping some heavy objects onto the sawhorse from a good height. First I dropped a safe, then a concrete block (which crumbled on hitting the sawhorse), then a small log. The top of the sawhorse ended up a little dented, but it withstood all three tests.
A friend remarked "why would you build sawhorses? I never use sawhorses".
I found that hard to believe, I use sawhorses quite a lot. Of the projects on this
website, this style of sawhorse appears on these pages