tightening efficiency each transverse cutout 13 is obtained on each flank 6 7 between the tip 11 and the rear 12 of the upper 2 in correspondence with the instep zone in this way the tightening has the effect of returning the wearer 39 s heel in the nesting of the rear 12 according to a construction detail visible in fig1 4 the thin flexible plate 18 includes a bead 31 which follows at least the contour of the edges 14 and 15 of the transverse is cutout 13 this bead 31 is inserted laterally between the edges 14 and 15 of the cutout 13 and the edges 16 and 17 of the movable flap 10 and has a height corresponding substantially to the thickness of the wall of the upper 2 in the location of the transverse cutout 13 and to the thickness of the wall of the movable flap 10 of course the boot according to the invention can include an inner comfort lining 33 as shown in fig2 and 3 particular accommodations such as aeration ventilation means or systems can of course be adapted to the tightening assembly described and in particular to the thin flexible plate 18 without departing from the scope of the invention likewise as shown in fig5 by way of example and for simplicity at least one thin flexible plate 18 can be made unitary with a flat and elongated portion 43 having a contour corresponding substantially to that of the foot which constitutes the 34 insole 34 advantageously in.