Designed for heavy duty truck and trailer shop use, rail and bus work, and portable for roadside service calls. Narrow chassis design fits easlity between tandem wheels. Chassis base is contoured so wheels make contact with ground when jack is not under load and raises them off the ground when under load to prevent damage. Wiper seals protect hydraulic system from contaminants. Overload and bypass safety valves prevent the jack from being used beyond its rated capacity and ram over extension.