manner similar to piston cylinder combination 28 includes a piston 58 which is movable in response to pneumatic control and includes inlet pneumatic means shown as tube 62 in order to move piston 58 towards the right from its initial position as shown in fig3 to one of its intermediate positions shown in fig5 a to its final position shown in fig5 b for moving lower clamping foot 14 away from upper clamping foot 12 and remove the fullness from material m in the direction of arrows 18 and to flatten the area around dart seam s as much as possible particularly in the area of the seam s to which the pocket welting will be adjacently placed to control the relative spacing between the upper and lower clamping feet adjusting screw 64 see fig1 has one end fixed to upper clamping foot 12 and lower clamping foot 14 is provided with a passageway through which the other end 65 of adjusting screw 64 passes for connection with collar 66 to provide for relative limited and controlled movement of lower clamping foot 14 relative to upper clamping foot 12 and a controlled change in the relative spacing between the upper and lower clamping feet in response to separation therebetween imparted by piston 58 lower clamping feet 14 also have a.