A longitudinal joint of the type forming a surface usable as a passage between a first passage surface and a second passage surface adjacent to one another, and usable as walking user passage, the distance between both surfaces in the longitudinal direction being variable, wherein said longitudinal joint - comprises a plurality of transverse slats attached to one another, having a substantially planar upper surface , - wherein each of said transverse slats is attached to the contiguous transverse slats by a pivot point with respect to which said transverse slats can rotate, maintaining the continuity of the surface of the longitudinal joint , - wherein the first passage surface comprises an inclined lower surface at its end, a certain number of transverse slats being hidden under said first passage surface , below the level of the upper surface of the longitudinal joint , by means of the relative rotation of the slats to one another with respect to the pivot point , depending on the distance existing between said first passage surface and the second passage surface , characterised in that - the longitudinal joint additionally comprises a first intermediate surface attached to the first passage surface , and a second intermediate surface attached to the second passage surface , configured for supporting the transverse slats , at least part of the second intermediate surface resting on the first intermediate surface , the support area between both surfaces being variable depending on the distance between the first passage surface and the second passage surface , and - in that the transverse slats additionally rest on curved support surfaces attached directlv to the first intermediate surface ; wherein the first intermediate surface is attached to the first passage surface . - comprises a plurality of transverse slats attached to one another, having a substantially planar upper surface , - wherein each of said transverse slats is attached to the contiguous transverse slats by a pivot point with respect to which said transverse slats can rotate, maintaining the continuity of the surface of the longitudinal joint , - wherein the first passage surface comprises an inclined lower surface at its end, a certain number of transverse slats being hidden under said first passage surface , below the level of the upper surface of the longitudinal joint , by means of the relative rotation of the slats to one another with respect to the pivot point , depending on the distance existing between said first passage surface and the second passage surface , characterised in that - the longitudinal joint additionally comprises a first intermediate surface attached to the first passage surface , and a second intermediate surface attached to the second passage surface , configured for supporting the transverse slats , at least part of the second intermediate surface resting on the first intermediate surface , the support area between both surfaces being variable depending on the distance between the first passage surface and the second passage surface , and - in that the transverse slats additionally rest on curved support surfaces attached directlv to the first intermediate surface ; wherein the first intermediate surface is attached to the first passage surface . <EOS>