When Hackworth got back to the post office and looked through the window of the big matter compiler, he saw a large machine taking shape in the dim red light. Its body had already been finished and was now rising slowly as its four legs were compiled underneath. Dr. X had provided Hackworth with a chevaline.
Hackworth noted, not without approval, that this one’s engineers had put a high priority on the virtues of simplicity and strength and a low priority on comfort and style. Very Chinese. No effort was made to disguise it as a real animal. Much of the mechanical business in the legs was exposed so that you could see how the joints and pushrods worked, a little like staring at the wheels of an old steam locomotive. The body looked gaunt and skeletal. It was made of star-shaped connectors where five or six cigarette-size rods would come together, the rods and connectors forming into an irregular web that wrapped around into a geodesic space frame. The rods could change their length. Hackworth knew from seeing the same construction elsewhere that the web could change its size and shape to an amazing degree while providing whatever combination of stiffness and flexibility the controlling system needed at the moment. Inside the space frame Hackworth could see aluminum-plated spheres and ellipsoids, no doubt vacuum-filled, containing the mount’s machine-phase guts: basically some rod logic and an energy source.
The legs compiled quickly, the complicated feet took a little longer. When it was finished, Hackworth released the vacuum and opened the door. “Fold,” he said. The chevaline’s legs buckled, and it lay down on the floor of the M.C. Its space frame contracted as much as it could, and its neck shortened. Hackworth bent down, laced his fingers through the space frame, and lifted the chevaline with one hand. He carried it through the lobby of the post office, past bemused customers, and out the door onto the street.
“Mount,” he said. The chevaline rose into a crouch. Hackworth threw one leg over its saddle, which was padded with some kind of elastomeric stuff, and immediately felt it shoving him into the air. His feet left the ground and flailed around until they found the stirrups. A lumbar support pressed thoughtfully on his kidneys, and then the chevaline trotted into the street and began heading back toward the causeway.
You’re going to give me a Diamond Age chevaline? Sign me up for two of them.
Eh. Stephenson never said it had to be practical.
In universe, the guy has this compiled (like 3D printing, but sci-fi and badass) at a public post office. This is a setting where nanotechnology is a consumer product. They have molecular gaskets and self-healing paper computers you can fold and crease without damage, and no doubt autorepairable machines. At one point in the book it’s explicitly shown that compiled objects can be easily decomplied in mere moments as well, so even if it’s got a service lifetime measured in single digit hours you could just chuck the thing into the deke hopper and rebuild it fresh and new.
Anyway, apparently the people in that setting have mastered durable synthetic molecular wonder materials, because Hackworth’s chevaline winds up patiently waiting for him essentially parked in a bush for an indeterminate number of years and still works just fine even with moss growing on it when he gets back to it.
(Also, ATM Machine.)