Abstract: A portable tool, such as a trimmer, with an output shaft locking pin disclosed. A gearbox of the portable tool includes a rotating shaft. A rotary member rotatable with the shaft is coupled to the shaft. A locking pin located along the exterior of the gearbox housing is constrained to move between at least two positions: a locking position and an unlocked position. In the locking position the locking pin extends below the gearbox housing to engage the rotary member mounted on the shaft, thereby locking the shaft. In the unlocked position the locking pin is retracted to avoid interference with the rotary member. The locking pin is biased to the unlocked position so that the top of the locking pin must be manually depressed to move and maintain the locking pin in the locking position.