They look like 'Jackall' style high-lifts, and yes they are used a lot around farms. Also used a lot in the world of off-road driving (every Landrover should have one!), and are usually very reliable if you avoid the cheapies. Not trying to sell one or anything, but those jacks work both ways so can also be used as a press or a winch, and can't (shouldn't) slip unless very worn or very overloaded.I guess the jacks are something 'special' that would be used on a farm or building site?