A set square for manual ceramic cutters, including a ruler intended to be rotatably mounted and secured to a base of a manual ceramic cutter, defining various angles; a stop that is mounted on the ruler and can be moved longitudinally; and a tightening element for securing to the ruler. The cross-section of the ruler includes two oblique planes that converge towards an intermediate surface provided with a longitudinal recess having a generally T-shaped cross section, for mounting the tightening element. The lateral stop includes two oblique planes facing the ruler and having the same slope as the oblique planes of the ruler, and which converge towards an intermediate surface that has an opening to mount the tightening element.