A profile bar to be locked to a panel, the profile bar comprising a frame (110) whose shape is a continuous profile extending in the longitudinal direction. Said frame further comprises: a slot (111) which is continuous in the longitudinal direction and in which the panel (100) can be installed; a first side (111 a) and a second side (111 b) of the slot, delimiting the slot and supporting the panel to be installed in it; and a protrusion (112) provided on the first side (111 a) of the slot and fitted to be placed in a groove (101) in the panel (100). The profile bar also comprises: a locking piece (200) comprising a locking part (230) which can be inserted between the panel in the slot and the second side of the slot (111 b), where said locking part is arranged to make the slot narrower, to push the panel against said protrusion and to support the panel in such a way that said protrusion remains in the groove (101) of the panel, wherein the detachment of the panel from the frame is prevented. A panel system c
