A form for casting pillars, of the type for which the assembly of two identical forms (10, 11) joined at an edge is provided by means of a threaded pin (12) which passes through a lateral upright (14) of a first form (10) with which it is associated and is designed to be inserted in a preset hole (15) of a series of aligned holes formed in the facing containment panel (16) and in one of the cross-members (17) for its support of a second form (11); the pin (12) is pulled by means of a nut plate (13) which is screwed to the threaded end portion (12a) of the pin (12) in order to lock the panel (16) of the second form (11) against the lateral upright (14) of the first form (10). The pin (12) is arranged within a cross-member (19) of the supporting frame of the containment panel (18), the cross-member (19) being constituted by a profile whose cross-section is shaped so as to prevent the rotation therein of the head (20) of the pin (12), the pin being free to perform a translational motion within the channel (21) of the profile in the direction formed by its axis, between a locking position, screwed onto the plate (13) and with the head (20) in abutment against the lateral upright (14) of the first form (10), and an inactive position, in which the threaded end (12b) of the pin (12) lies inside the upright (14), while the head (20) rests against an extraction-preventing abutment (22) provided within the channel (21) of the profile.