The injured employee was assisting with tightening down 3/4" hardware during assembly of a 6'x20' triple deck screen. Another employee was using a 1/2" cordless impact wrench to tighten down the hardware. The injured employee was using a 1-1/8" open-end wrench that slipped when the bolt was being tighten down by the impact wrench. The injured employee's right ring fingertip was caught between the open-end wrench and the side sheet of the triple deck screen. The tuft of the distal phalanx was amputated.