Abstract: Process for reducing the height of a box to the level of the apex of the stack of objects therein, wherein horizontal score lines are made at a height substantially equal to that of the apex of the stack of objects and such that the distance between the apex and the top of the box is greater than the half-width of the box. During a phase of simultaneous folding of the upper parts of the two side walls parallel to the length of the box toward the centre thereof, and before the upper edges or ridges of the upper parts meet, the angles of inclination of the upper parts are differentiated with respect to one another so that, when the upper parts meet, the upper edge of one covers the upper edge of the other, the upper parts sliding over one another during the final phase of folding the latter.