 In industrialised countries they are no longer used for commercial purposes, but preserved examples can often be seen at steam fairs driving appropriate equipment for demonstration purposes.Portable engines during their heyday were typically towed to their work sites by draft horses or oxen, or, in the latter part of that era, motive power including self-propulsion or towing by traction engines, steam tractors, other tractors, or trucks.They were used to drive agricultural machinery (such as threshing machines), milling machinery (such as gristmills, sawmills, and ore mills), pumps and fans (such as in mines and oil wells), and factory line shafts (for machine tools, power hammers, presses, and other machines).