spring effect which light though it may be is sufficient to press free strip 62 against the floor by means of the adhesive this effect is improved if during fitting the user progressively removes protection strips 64 longitudinally as the fitting progresses if desired the user may first glue one of the two sides and press on it then glue the second one as described hereabove once the threshold bar has been glued pressure applied thereon crushes the fold and suppresses any extra thickness support material 66 of the adhesive film may be a paper or plastic sheet the use of plastic has the advantage of providing an additional resistance and a better spring effect during fitting as a variation other materials may be used for example a metal or composite sheet fig6 is a view in position of another embodiment of a threshold bar 5 also illustrating some variations in the example of fig6 it is assumed that there is a need to adjust the level between two floor coverings 12 and 13 laid on a floor 11 gluing strips 62 g to the left in the orientation of the drawing and 62 d to the right in the orientation of the drawing rest by their adhesive layers on floor coverings 12 and 13 and provide a gluing of threshold bar 5 with no extra thickness fig6 illustrates a first variation according.