A homemade sawhorse could be the least expensive element of your workshop. It's also easy to create and will last almost indefinitely. Measuring and cutting long lengths of lumber is much easier if the lumber is stacked across two sawhorses, and they can also be used to support scaffolding planks that will allow you access to almost any part of a one-story building. These are invaluable tools, and you fortunately will never have to go without one if you follow these steps.
Step 1 - Assemble the Crossbeam or "Back"
The sawhorse can be built to any length, but the height is fairly standard. Six eight-foot, 2x4 wood studs will provide enough material to build a four-foot-long sawhorse. You will assemble the sawhorse using #16 nails.
To begin, cut three 2x4 boards each to a length of four feet. Position one of the boards so that the two-inch edge is perpendicular on top of the flat, four-inch side of the second board, forming an elongated “T”. Nail through the outer width of the first board, into the edge of the second board, to join them together. Leave one foot of spacing between the nails as you go. Take the remaining four-foot board and place its four-inch width flat against and parallel to the opposite edge of the middle board. Attach with nails, as described, so the entire assembly resembles a small wooden, I-shaped beam.
Step 2 - Attach the Legs
Cut four legs from the four-foot-long 2x4 boards. At both ends of the I-beam and on each side, angle the top end of each leg into the U-shaped pocket that is flat against the side of the I-beam, so that it butts up under the top flange (top horizontal component) and the web (vertical component). This will cause the legs to angle outward from the I-beam at about 40 degrees from each other. Drive five nails through the top end of each leg into the web and the bottom flange to connect the legs firmly.
Step 3 - Install Bracing
These will also act as a step for climbing up and standing atop the I-beam, so install them at a height that feels comfortable. Cut 2x4 that will brace the legs diagonally to the I-beam. Nail one end flat to the outside surface of each leg at about 1/3 the height of the leg and the other end near the center of the I-beam. Brace all four legs in this way.
Cut lengths of 2x4 for the horizontal leg bracing next. Install these flat against the legs at a height about midway between the ground and the top of the I-beam. These boards will wrap around all four legs to form a rectangle, bracing each leg to the adjacent leg. Nail them securely to the legs.
Step 4 - Try it Out
Set the sawhorse on a level surface and check to see if it rocks. If necessary, trim the legs until it stands firmly on all four legs. If the sawhorse is to be left outdoors, exposed to the elements, you can make it from pressure-treated lumber or you can apply a protective wood finish after you're done.