will of course be anticipated in a non limiting manner the percentage of contraction of this type of textile material is on the order of 5 to 10 in a fifth step frame 2 is attached to support 3 in the form of a partition or ceiling this frame 2 consists of retaining profiled sections 2 u2032 for example four of them each having for example two opposite clamping jaws not represented these retaining profiled sections 2 u2032 are arranged so as to form a closed frame retaining profiled sections 2 u2032 can also be attached to different supports 3 in order to produce a panel 1 between two walls or a panel 1 installed vertically on the floor in a sixth step the peripheral edges of the sheet are engaged between the clamping jaws of retaining profiled sections 2 u2032 the sheet secured along its peripheral edges is pre stretched when it is placed on frame 2 in a seventh step the sheet is heated locally at the places having folds or lack of tension in order to bring about heat shrinking of the flexible textile material to do this the heating end of a heat gun mounted for example on a mobile carriage is positioned at distance of approximately 20 to 30 cm from the sheet facing the predetermined zone of the sheet that is to be tightened the heat gun is possibly moved to a second zone preferably the heat gun is moved for example according to a straight line trajectory shifted from one line to another for the purpose.