A flange for guiding a protective screen, in particular for a roller shutter, in which: - the flange comprises a sleeve, which delimits an internal volume extending along a fitting axis and which is configured to receive a winding tube of the screen when this winding tube is fitted into the sleeve, where - the flange further comprises a locking part on the winding tube fitted into the flange, the locking part comprising: • at least one first locking member, configured so as, in an engaged configuration, to secure the locking part and the winding tube in translation along the insertion axis, characterised in that - the locking part also comprises: • at least one second locking member (68A, 68B), configured so as, in an engaged configuration, to secure the locking part and the sleeve in translation along the insertion axis, - the locking part is configured to pass: • an unlocked configuration, in which the locking part is free to move in translation relative to the sleeve along the insertion axis and in which the first and second locking members are not in the engaged configuration, • to a locked configuration, in which each second locking member is in the engaged configuration, the locking part being linked in translation with the sleeve and with the winding tube along the insertion axis, - the change from the unlocked configuration to the locked configuration is made by reversibly clipping the locking part onto the sleeve. - the flange comprises a sleeve, which delimits an internal volume extending along a fitting axis and which is configured to receive a winding tube of the screen when this winding tube is fitted into the sleeve, where - the flange further comprises a locking part on the winding tube fitted into the flange, the locking part comprising: • at least one first locking member, configured so as, in an engaged configuration, to secure the locking part and the winding tube in translation along the insertion axis, • at least one first locking member, configured so as, in an engaged configuration, to secure the locking part and the winding tube in translation along the insertion axis, - the locking part also comprises: • at least one second locking member (68A, 68B), configured so as, in an engaged configuration, to secure the locking part and the sleeve in translation along the insertion axis, • at least one second locking member (68A, 68B), configured so as, in an engaged configuration, to secure the locking part and the sleeve in translation along the insertion axis, - the locking part is configured to pass: • an unlocked configuration, in which the locking part is free to move in translation relative to the sleeve along the insertion axis and in which the first and second locking members are not in the engaged configuration, • to a locked configuration, in which each second locking member is in the engaged configuration, the locking part being linked in translation with the sleeve and with the winding tube along the insertion axis, • an unlocked configuration, in which the locking part is free to move in translation relative to the sleeve along the insertion axis and in which the first and second locking members are not in the engaged configuration, • to a locked configuration, in which each second locking member is in the engaged configuration, the locking part being linked in translation with the sleeve and with the winding tube along the insertion axis, - the change from the unlocked configuration to the locked configuration is made by reversibly clipping the locking part onto the sleeve.