1. IN A MACHINE FOR SECURING THE PERIPHERY OF A PANEL OF SCREEN MATERIAL IN A CHANNEL EXTENDING LONGITUDINALLY ALONG THE UPPER FACE OF A SIDE BAR OF THE FRAME FOR THE SCREEN, AND WITH AN EDGE OF THE SCREEN MATERIAL OVERLYING THE SAID FRAME BAR AND THE SAID CHANNEL; THE COMBINATION OF A MACHINE FRAME, MEANS FOR SUPPORTING THE SCREEN ON SAID MACHINE FRAME, MEANS FOR SUPPORTING AND ADVANCING THE SCREEN FRAME ALONG A FIXED PATH SO THAT THE SAID FRAME BAR MOVES LONGITUDINALLY ALONG ITS OWN AXIS, SAID SUPPORTING AND ADVANCING MEANS INCLUDING A BELT WHICH MEANS FOR GUIDING AND SUPPORTING SAID BELT IN CONTACT WITH THE SCREEN FRAME TO ADVANCE THE SAME ALONG A LINE IN WHICH THE CHANNEL EXTENDS AND INTO WHICH THE TUCKER ROLLER FORCES THE EDGE PORTION OF THE SCREEN MATERIAL, ANND AN ELECTRIC MOTOR WITH A DRIVE-PULLEY DRIVEN THEREBY, SAID DRIVE-PULLEY LOCATED IN A DOWNWARDLY EXTENDED LOOP OF SAID BELT, AND MEANS ACCESSIBLE TO THE OPERATOR FOR CLOSING A STARTING CIRCUIT FOR SAID MTOR; A HOLD-DOWN CARRIAGE NORMALLY SUPPORTED ABOVE THE CHANNEL WITH MEANS FOR GUIDING THE CARRIAGE DOWN TO THE CHANNEL, A HOLD-DOWN DISC-FORM ROLLER ROTATABLE FREELY ON ITS OWN AXIS ON THE HOLD-DOWN CARRIAGE, AND SO AS TO ROLL ON THE SCREEN MATERIAL AT THE EDGE OF THE CHANNEL ADJACENT TO THE BODY PORTION OF THE SCREEN MATERIAL; AND MEANS FOR ADVANCING SAID CARRIAGE SO AS TO PRESS THE EDGE OF THE HOLD-DOWN ROLLER FORCIBLY AGAINST THE SCREEN MATERIAL AND THEREBY HOLD THE SAME FIXEDLY PRESSED AGAINST THE SAID SIDE BAR AT A POINT ADJACENT THE SIDE OF SAID CHANNEL THAT IS LOCATED TOWARD THE INNER AREA OF SAID SCREEN MATERIAL, A TUCKER-CARRIAGE SUPPORTED ON THE MACHINE FRAME, WITH A TUCKER DISC-FORM ROLLER ROTATABLY SUPPORTED AT ITS OWN CENTRAL AXIS ON THE TUCKER CARRIAGE WITH THE PERIPHERY OF THE TUCKER ROLLER LOCATED APPROXIMATELY IN THE VERTICAL PLANE IN WHICH THE LONGITUDINAL AXIS OF SAID CHANNEL LIES; MEANS OPERATING AFTER THE HOLD-DOWN ROLLER IS HOLDING THE SCREEN MATERIAL FIXEDLY ON THE SCREEN FRAME, FOR ADVANCING THE TUCKER CARRIAGE TOWARD THE CHANNEL SUFFICIENTLY TO ENABLE THE EDGE OF THE TUCKER-ROLLER ADJACENT THE CHANNEL TO FORCE THE EDGE PORTION OF THE SCREEN MATERIAL DOWN INTO THE CHANNEL TO CAUSE THE SCREEN MATERIAL DISPLACED BY THE EDGE OF SAID TUCKER-ROLLER TO CONFORM GENERALLY TO THE CROSSSECTION OF SAID CHANNEL AND DEVELOP AN INSET FLANGE COMPOSED OF THE SCREEN MATERIAL LYING WITHIN THE SAID CHANNEL IN SAID FRAME BAR OF SAID SCREEN FRAME; A SPLINE ROLLER HAVING A PERIPHERAL GROOVE FOR CARRYING AND GUIDING A CONTINUOUS STRIP OF SPLINE, A SPLINE ROLLER CARRIAGE ON WHICH THE SPLINE ROLLER IS ROTATABLY MOUNTED, MEANS FOR MOVING SAID SPLINE ROLLER CARRIAGE ON SAID MACHINE FRAME, DOWN TO THE WORK, MEANS FOR CONTINUING THE ADVANCING MOVEMENT OF SAID SCREEN-FRAME TO BRING THE SAID INSET FLANGE OF THE SAID SCREEN MATERIAL ABREAST OF THE LOCATION OF THE SPLINE ROLLER AND ITS CARRIAGE, AND THEREBY COOPERATING WITH THE ADVANCE OF THE WORK TO ROTATE THE SPLINE ROLLER, AND TO INTRODUCE THE GROOVED EDGE OF THE SPLINE ROLLER DOWN TO SAID INSET FLANGE THAT IS COMPOSED OF THE SCREEN MATERIAL, AND TO COMPRESS THE SPLINE CARRIED ON THE PERIPHERY OF THE SPLINE ROLLER AND TRANSFER THE SAME INTO CONTACT WITH THE SAID INSET FLANGE COMPOSED OF THE SCREEN MATERIAL; AND MEANS FOR WITHDRAWING THE SPLINE CARRIAGE WHEN THE ADVANCING SCREEN FRAME HAS PASSED THE LOCATION OF THE SPLINE ROLLER, AND TRANSFERRED THE SPLINE TO THE FULL LENGTH OF THE CHANNEL ON THE SAID FRAME BAR.