The invention relates to a slat (1) for Venetian blinds comprising a profiled element which extends in a main direction of longitudinal extension X with two opposite longitudinal edges (2,3) and which defines the body of the slat, said slat (1) comprises along each longitudinal edge a plurality of through holes (10) made on the profiled element, each hole opens onto the outside of the slat (1) by means of a slit (11) which extends from the hole as far as the nearest longitudinal edge, wherein each hole acts as a housing seat for a support half-ladder (40) of the slat (1), wherein each slit (11) defines on the profiled element at least one portion (20) movable between a raised position, in which it is raised in relation to the profiled element so as to distance the lips of the slit from each other and permit the insertion of the half-ladder in the respective hole, and a lowered position, in which it is lowered onto the profiled element so as to close the slit and retain the half-ladder inside the hole.