and the lower contact surfaces 45 of the locking system are also plane and parallel with the plane of the floorboard in the joined position according to fig5 the two juxtaposed upper portions 41 and 42 of the surfaces facing each other of the boards 1 1 u2032 define a vertical joint plane f fig6 shows an example of an embodiment according to the invention which has not yet been published and which differs from the embodiment in fig5 by the tongue 38 and the tongue groove 36 being displaced downwards in the floorboard so that they are eccentrically positioned moreover the thickness of the tongue 38 and thus the tongue groove 36 has been increased while at the same time the relative height of the locking element 8 has been retained both the tongue 38 and the material portion above the tongue groove 36 are therefore significantly more rigid and stronger while at the same time the floor thickness t the outer part of the strip 6 and the locking element 8 are unchanged fig7 shows a first embodiment of the present invention the locking element 8 has a locking surface 10 with a locking angle a which is essentially perpendicular to the plane of the floorboards the locking surface 10 has been moved upwards relative.