I visited one retrofit workshop run by a strict Mennonite. Marlin was a short beardless man (no beards for the Mennonites). He uses a horse and buggy, has no phone, but electricity runs in the shop behind his home. They use electricity to make pneumatic parts. Like most of his community, his kids work along side him. A few of his boys use a propane powered fork lift with metal wheels (no rubber so you can't drive it on the road) to cart around stacks of heavy metal as they manufacture very precise milled metal parts for pneumatic motors and for kerosene cooking stoves, an Amish favorite. The tolerances needed are a thousand of an inch. So a few years ago they installed a massive, $400,000 computer-controlled milling (CNC) machine in his backyard, behind the horse stable. This massive half-million dollar tool is about the dimensions of a delivery truck. It is operated by his 14-year old daughter, in a bonnet. With this computer controlled machine she makes parts for grid-free horse and buggy living.