A dobby lever which is insertable into a main lever of a textile loom includes a sliding nut to set and adjust its position along the main lever. The dobby lever has a pair of parallel flat sides, separate but fixed to each other. The sliding nut has a body which can be inserted between the sides of the main lever. The body of the sliding nut has a hole at one end for receiving a joint which can be connected to a driving bar and a blocking device at its other end for the sides of the main lever. The body at the other end has sloping surfaces, and wedge-shaped elements are provided having complimentary slanting surfaces which are insertable into a box-shaped container and act upon the sides of the main lever. A screw element is insertable into the box as a blocking device to adjust the position of the wedge-shaped elements with respect to the sloping surfaces of the body and the sides of the main lever, and a connecting element freely joins and holds the wedge-shaped elements together relative to the sloping surfaces of the body of the sliding nut.