A semi-trailer landing gear apparatus employing a handheld power tool is disclosed. The landing gear apparatus is attached to a standard landing gear drive shaft. The landing gear apparatus includes a slip collar drive that allows an operator to use the power tool without removing the hand crank. The power tool has a locking blade which slides into or otherwise engages with a trailer-mounted bracket or bracket mounted on a telescoping arm when the coupler is engaged, preventing rotational movement against the operator as the motor is activated. The power tool also has a quick-release socket assembly which readily connects and disconnects the power tool from the apparatus. A planetary gear system is employed for gear reduction within the power tool. The apparatus may employ a trailer-mounted motor to raise and lower the trailer landing gear.