Abstract: A jack assembly includes a base, a support platform, a pair of links connecting the base to the support platform and an actuator connected between the base and the support platform. The actuator is operable to move the support platform between lowered and raised positions. The actuator may be coupled to a power assist cylinder which utilizes pressurized compressible fluid to assist in lowering the support platform. A safety lock system includes a lock bar pivotally connected to the support platform and one or more pockets on the base positioned to receive a free end of the lock bar to retain the support platform in a selected raised position. A preferred support platform includes trays which receive contact blocks selected from a set of varied contact blocks. A portable automobile lift comprises a pair of the jack assemblies in combination with a portable power unit.