A Line Mechanic reports the tail cone on a B737-800 aircraft was damaged by a lift truck platform while he was attempting to retract the truck's outriggers.

Narrative

I was assigned to work on a B737-800 aircraft. I was performing the Elevator Hinge Inspection Workcard. I needed a [personnel] lift to perform the job and could not find a smaller lift. I had to use the larger lift truck which had a platform that covered both sides of the elevator access hinge panels. Upon completion; I was operating the same switch on the lift truck; which I used to lower the outriggers. I was on my knees to watch the outriggers retract. I heard a cracking sound and immediately released the switch. I walked around the work area and discovered that the platform had raised up and struck the tail cone of the aircraft. I had no formal training on this equipment and was mislead by the labeling of the controls of the outriggers and platform. This lift truck was different from the smaller lift trucks in that; the outriggers on the smaller lifts had a separate switch that controlled the outriggers only. This larger lift that was in use had a switch that operated both the platform and the outriggers.