Tri-horses are designed to be cut from a double-layer of 3/4-inch plywood. The components shown here are enough for one 4-foot and one 8-foot Tri-Horse.
This is one way to set up a mobile shop. Note the various home-made attachments for supporting saws and stock. There’s no reason the saws couldn’t be turned to face the opposite direction or that longer or shorter horses couldn't be used for either leg.
In this photo Tri-Horses are being used as traditional sawhorses—probably the least likely way for them to be used since there are so many other ways to support material. The best use for Tri-Horses is as part of a work station.
This is an interesting setup because instead of a plywood top rail that curves down to land on the floor, the top rail on this work station is a 2x10 or 2x12 supported by plywood leg sections. This would likely be an easier and more economical build than a conventional Tri-Horse, but perhaps not as stable on uneven ground (because it has four rather than three points of contact).
The plans consist of a 12-page PDF that sells for $10. They include detailed instructions on how to build Tri-Horses and suggestions for how they might be customized. These are the main components and one suggestion for how they might be combined.