Pliers for tightening parts for levelling cladding tiles, in particular for a pushing wedge (C) and a levelling element (E); said pliers comprising: - a first arm , straight, having a handle on a rear end and a guide bar on a front end for the movable assembly of a supporting stop of the levelling element (E); - a second arm , at an angle, having a rear end provided with a handle and having a contact surface with the pushing wedge (C) on a front end; - a rotation shaft relative to the arms of the pliers; and - means for fastening the supporting stop in different positions along the guide bar of the first arm ; - wherein the supporting stop comprises: a passage with a height greater than the guide bar; and a shaft assembled in a longitudinal slot of the guide bar which enables a longitudinal movement of the supporting stop along the guide bar ; and - wherein the means for fastening the supporting stop in several positions longitudinally spaced with respect to the guide bar are made up of a straight pawl comprising: a row of teeth defined along the guide bar , and a stop or tab assembled in the supporting stop and able to be housed between any two consecutive teeth of the guide bar ; characterized in that: - the shaft assembled in the longitudinal slot of the guide bar further enables relative rotation of the supporting stop with respect to the guide bar between a fastening position, in which the stop or tab is housed between any two consecutive teeth of the guide bar , and a longitudinal movement position, in which the stop or tab is arranged spaced from an end of the teeth ; and - the supporting stop further comprises a spring which acts against a supporting surface of the guide bar and tends to maintain the supporting stop in the fastening position with respect to the guide bar . - a first arm , straight, having a handle on a rear end and a guide bar on a front end for the movable assembly of a supporting stop of the levelling element (E); - a second arm , at an angle, having a rear end provided with a handle and having a contact surface with the pushing wedge (C) on a front end; - a rotation shaft relative to the arms of the pliers; and - means for fastening the supporting stop in different positions along the guide bar of the first arm ; - wherein the supporting stop comprises: a passage with a height greater than the guide bar; and a shaft assembled in a longitudinal slot of the guide bar which enables a longitudinal movement of the supporting stop along the guide bar ; and - wherein the means for fastening the supporting stop in several positions longitudinally spaced with respect to the guide bar are made up of a straight pawl comprising: a row of teeth defined along the guide bar , and a stop or tab assembled in the supporting stop and able to be housed between any two consecutive teeth of the guide bar ; - the shaft assembled in the longitudinal slot of the guide bar further enables relative rotation of the supporting stop with respect to the guide bar between a fastening position, in which the stop or tab is housed between any two consecutive teeth of the guide bar , and a longitudinal movement position, in which the stop or tab is arranged spaced from an end of the teeth ; and - the supporting stop further comprises a spring which acts against a supporting surface of the guide bar and tends to maintain the supporting stop in the fastening position with respect to the guide bar . <EOS>