There seem to be thousands of different plans for sawhorses out there, and it seems that people especially love making ones that are ludicrously sturdy. That's cool and all, but the last thing I need in my less-than-half-a-garage workshop is some beefy sawhorses using up precious floor space. These ones are light, easy to make, can be hung on the wall, and one of them can support ~500 lbs (3 people) and still feel rock solid. The chances of me lifting something heavier than 1000 lb on to my pair of sawhorses are frankly pretty low...
Step 1: Design and Materials
Sawhorses meant for a building site are overengineered and impractical for a workshop where space is at a premium. My design was strongly influenced by the fact I had a 3' × 4' sheet of plywood left over from a deck build that used 5' × 4' sheets, and 3' is roughly how high and how long I wanted the sawhorses to be. They needed to be light and strong and be able to fold flat.
No one ever builds a single sawhorse, and I'm no exception. I built two, but after finishing them, I redesigned them to be slightly smaller so that four could be cut out of a single sheet of plywood, with enough plywood left over to build two sets of hangers. However, the exact size is far from critical, and if you want a different size, you know what to do (if you don't know what to do, I suggest you simply buy some - there are lots of nice light inexpensive folding sawhorses out there).
In addition to the 3/4" construction plywood, I also used 4 recycled 3 1/2" door hinges, wood glue, 1 1/4" drywall screws, 2" deck screws and some 1/4" (6 mm) polypropylene rope. These sawhorses would still be strong enough for most purposes if built with 5/8" or even 1/2" plywood.
I'm fortunate enough to have a table saw and a miter saw, and made all the cuts with these. However, none of the cuts are complicated and you can easily angle the blade on a circular saw (like the one I have) to make the necessary cuts. I don't recommend making this design if you only have a handsaw or jigsaw, make one out of lumber instead.
A SketchUp file for the sawhorse is attached to this step, so you can easily tweak the design to suit your own needs.
Step 2: Cut
My hinges were 89 mm (3 1/2") wide so I used that as a guide to the width of each piece. Note that the dimensions that I list here are for sawhorses whose size has been tweaked so that four can be cut from a single sheet of plywood; they're not quite the same as the ones I built. But that's OK - mine are (like me) unusually tall and most people would prefer slightly shorter ones anyway.
8 pieces of 844 × 90 mm (33 1/4" × 3 1/2") crosscut at 20 degrees on each end (parallel). These are the legs.
2 pieces of 844 × 90 mm (33 1/4" × 3 1/2") cut square. These are the tops of the sawhorses.
2 pieces of 844 × 180 mm (33 1/4" × 7"), which you need to rip down the middle at 20 degrees, to make four pieces with one angled edge. These are the upper crosspieces.
4 pieces of 711 × 180 mm (28" × 7"). which you need to rip down the middle at 20 degrees, to make four pieces with one angled edge. These are the lower crosspieces.
The second picture is the cutting diagram for getting four sawhorses and two sets of hangers from a single sheet of plywood. The wide pieces need to be ripped down the middle at 20 degrees to make the crosspieces. Green: tops. Yellow: lower crosspieces. Tan: upper crosspieces. Blue: legs. Pink: parts for making hangers. White: waste. I suggest starting with the longitudinal cut that runs between the yellow and tan parts. A 4 mm kerf has been allowed for.
Step 3: Assemble
I cut a piece of plywood 80 × 200 mm* to act as a story stick - it gave me the two critical dimensions for assembly, the distance the top crosspiece protruded past the legs and the distance from the bottom of the leg to the bottom of the crosspiece. I worked out where I needed to drill the holes in the legs (making sure they weren't going to clash with the hinge screws) and made five in a cross shape for each joint. I used that piece as a template for the other 7 legs, and then countersunk all the holes. I drilled through the legs into the cross pieces so that the fasteners were less obvious. I then glued and screwed all four pieces together (ensuring squareness at each step) and repeated 3 more times to make the four halves. I used plenty of wood glue and 1 1/4" drywall screws. 1 1/4" drywall screws are not especially strong but with a gluing area for each joint of >12 square inches, I wasn't concerned - the glue does all the work. I could probably have done it with my nailgun but the nails I had were too short.
* if you make this according to the SketchUp plan, the story stick should be 67 × 190 mm (2 5/8" × 7 1/2").
Step 4: Hinges, Top, Rope
I added the hinges to each leg, making sure they didn't protrude above the top of the sawhorse. I then set the sawhorse in open form and screwed the top piece to one side of the frame. I didn't glue this, because I figured it might be good to be able to replace this bit in future when it gets banged up. I then went over the whole thing with an orbital sander and removed all the sharp edges.
I wanted more support to stop the sawhorse opening any wider than 20 degrees, so drilled holes through each leg at the joint and threaded a piece of polypropylene rope through the holes, and knotted the ends at a point where the legs were fully open. I then melted the knots with a lighter to ensure they weren't going to come untied. Polypropylene is not stretchy, is inexpensive and is exceedingly strong.
Step 5: Hangers
Now that you have made your sawhorses, you will want to hang them up out of the way when you're not using them. Here is a simple plan to make hangers out of a few plywood offcuts. Cut two rectangles of dimensions 188 × 50 mm (7 3/8" × 2"), and two of dimensions 206 × 50 mm (8 1/8" × 2"), and two right-angled triangles 188 × 188 mm (7 3/8 × 7 3/8"). Glue and screw (I used 2" drywall screws) these together as shown, then screw the hangers to the wall into a pair of adjacent studs (I used 3" deck screws). If you made four sawhorses out of a single sheet of plywood, your offcuts will be big enough to make the hangers as well (see cutting diagram in Step 2).