by a roll preferably made of stainless steel having a diameter of between 200 mm and 1 000 mm and is rotated by any suitable means so as to have a peripheral speed equal to the speed at which the material 2 enters the installation in general this speed is between 10 m min and 200 m min and the increase in speed from one roll to the next is about 0 5 to 3 the perforations 10 of which the roll consists are of cylindrical or honeycomb shape said roll being advantageously covered with a fabric made of steel monofilament or of plastic or with a perforated sheet having a porosity of between 3 and 20 this element is not shown in fig2 the injection rail or injector r which is placed so as to be parallel to a generatrix of the roll c is a conventional injection rail which creates water jets or needles 11 at a usual pressure of at least 30 bar sometimes more so as to entangle the elementary fibers of the web 2 such an injector may be designed in a manner similar to the teachings of ep a 0 400 249 inside the roll c is placed a suction box 12 which is fixed coaxial with the rotating roll c and connected to a suction source which allows a partial vacuum to be created inside said box this fixed suction box 12 has in alignment with the water jets 11 a slot 13 approximately 10.