Equalizer Single Leg Hydraulic Trailer Jacks and Hydraulic Trailer Jacks Hydraulic jacks are the fastest and easiest way to load and unload your trailer from the tow vehicle. These can be utilized in a single or dual jack application which make it easier to level the front of your trailer. These systems are operated off the trailer's accessory battery. They can be installed by a manufacturer, dealer, service /repair center, or by the customer. The hydraulic jacks are offered in various sizes and lifting capacities.