Back in the olden days machinery didn’t have their own engines. Machinery was hooked up to an engine by a large belt and pullies. If you couldn’t get the person who owned the engine to show up when you wanted you couldn’t run your equipment as few farmers owned their own engines and rented them.

Here’s a photo of an engine. The engine would go around to farms and run the thrasher or other equipment. As the equipment did not have their own engine or motor. A large belt would run from the engine to the equipment by pullies on each end.