An articulated robot including a vertical rod secured with lockbolts at the end of its arm which is fixed to a screw fastening unit by means of an upper bracket and a lower bracket. The robot further includes a studbolt parallel to the vertical rod at the lower end of the arm. Two nuts are mated with the studbolt to compress the lower bracket. Releasing the lockbolt and rotating the nuts clock-wise or counter-clockwise causes the vertical rod to easily slide to adjust the height of a screw fastening unit from workpieces of different types without having the operator hold the screwing unit by hand.