An employee was aligning the attachment coupler pin boss on a skid steer to pin the bucket cylinder rod end to the skid steer. The coupler was partially raised off the floor, and synthetic blocking was placed beneath it. A floor jack was then placed beneath the coupler to make final adjustments, aligning the pin boss and the cylinder rod end for pinning. While on his knees, the employee operated the floor jack with his left hand and had his right hand on the coupler pin boss for balance. The jack shifted, causing the pad of the employee's fingertip to become pinched between the pin boss and the cylinder rod end. The employee suffered an amputation of tissue on his finger pad that required surgery to reattach.