of the opening of the sheath once the lancet l has made contact with the needle a as shown the device is displaced in the direction v fig6 that is to say in the direction of the eye c of the needle a first over the cylindrical part of the needle then in the groove r fig7 and 10 which every sewing machine needle has and at the end of this groove in front of the eye c of the needle the lancet l then penetrating the eye under the action of the spring entraining with it the thread f the groove r thus ensures the guiding of the lancet l toward the eye c the user continues to apply pressure on the sleeve 3 initially to bring it into the position visible in fig7 and 8 in which the sleeve comes into contact with the segments f1 and f2 of the thread f projecting on either side of the base of the slit 7 the angular position of the device is adjusted as necessary relative to the needle a so that the lancet and the groove r of the needle as well as the eye become coplanar from this moment the sleeve 3 pushes the thread first out of the slit 7 so that it becomes free of.