Abstract: At 8:00 a.m. on September 28, 2020, Employee #1, a carpenter employed by Brco Constructors Inc., was working on a school construction project in Dixon, CA. The employee was using a Hitachi Koki NR 90AC3 pneumatically-driven nailer to frame windows while working from an aerial device approximately 8-10 feet off the ground. While positioning plywood with one hand, the employee accidentally pointed the nailer toward his own body. This resulted in a ring-shank nail being discharged into his knee. The employee experienced immediate pain and was unable to move his knee. The supervisor was called to the scene, assessed the situation, and called emergency services. Emergency personnel arrived within 10 minutes and transported the employee to Kaiser Vacaville, where surgery was performed to remove the nail. The employee was hospitalized. The investigation revealed that the employee had not been provided with the operator's manual for the nailer, which would have outlined the hazards associated with its use.