conduit 136 into the conduit 134 and thus to the pilot port of the valve 46 which acts to port air to the tail end of the pneumatic piston cylinder 54 when supply air is attached to the fitting 104 air fed from the port 108 to the supply port of the valve 46 communicates air to the head end of the cylinder to drive the upper rack 32 and the needle 12 forwardly when the trigger 142 is mashed or squeezed the valve 138 permits air to flow through the port 132 to the pilot port of the valve 46 this acts to exhaust air from the head end and supplies the air to the tail end to drive the upper rack 32 and the needle 12 rearwardly of course as the needle goes forwardly the yarn grasping plunger 70 moves rearwardly and as the needle moves rearwardly the yarn grasping plunger 70 moves forwardly to grasp a loop of yarn when the trigger is released the valve 138 closes the communication between the conduit 136 and the conduit 134 and the air supplied from the portal 108 to the supply port of the valve 46 again drives the needle 12 forwardly as air is exhausted from the tail end of the cylinder through the second exhaust port in operation an operator prior to mashing the trigger 142 may insert the point of the needle into the backing material of the carpet thereafter squeeze the trigger 142 to drive the plunger forwardly and the needle rearwardly so that the slotted portion 72 of the plunger grasps the loop of yarn and holds it and upon release of the trigger the plunger moves rearwardly and the.