This line was designed for assembly of railway car underframes of passenger car types 4440, 4441, 4444, 4447  The jig line is a  framework where guides with T-type slots as well locators and clamping elements are fixed. While readjusting of the line for some frame dimension-type locators and clamping elements  move along the T-slots. Constituents of a piece are clamped by pneumatic actuators. The use of a pneumatic system ensures a even clamping of all the constituents.