14 16 takes place they are jammed against the thread flanks at a a b b c c and d d no further rotation takes place and more importantly no reverse rotation takes place because of the high frictional contact between the washer 50 and the faces 24 44 rotation of the lead screw 10 in the direction of the upward facing arrow l i e clockwise when viewed from the right in fig3 will cause the nut halves to move toward the right as a unit carrying whatever load is attached to the face plate 18 on the nut half 14 upon the end of the traverse of the lead screw 10 to the right with the nut half 14 pushing the nut half 16 to the right as viewed in fig3 the length of the lead screw the direction of the lead screw is reversed at that time the thread flanks are still in engagement at c c d d and there will be no lost movement because of backlash since these surfaces are already in intimate contact the nut halves being biased in such a manner creates a wedging effect and locking of the two nut system if wedging did not occur the nuts would act independently of each other and backlash due to gaps between the thread flanks would take place the load applied to the left nut half 14 or mounting nut would merely cause the right nut half 16 to.