Transverse longitudinal joint comprising slats (11) with a main shaft (11e), a passable surface (11s), a functional surface (11f) opposite to the passable one (11s), connecting sides between the passable (11s) and the functional (11f) surfaces. Slats are mounted one after the other according to the main shaft (11e) to form a bellows structure, with a displacement movement without break in continuity with 2 degrees of freedom, so as to modify the bellows shape between an unfolded position and a folded position. Slats form a retractable surface (1). Each intermediate slat (11) has joining elements having: a male end (11A) in a first connecting side; a female end (11B) in a second connecting side, opposite to the first connecting side; the female end (11B) receives the male end (11A) of an adjacent slat (11).