Employees were repairing a headache rack for a pickup truck. The headache rack was taken off the truck and placed on jack stands; however, the headache rack was not level. The employees attempted to level the headache rack by placing another jack stand under the rack. As the jack stand was being placed under the headache rack, the rack fell off the jack stands. An employee was on top of the headache as it was being leveled. The employee fell off the rack and landed on wooden pallets that were next to the rack. The employee suffered a back injury and was admitted to the hospital.