Abstract:
Gallery mounting of a sheet on a substrate is performed by placing a corner edging around the substrate peripherally. The sheet is positioned on a bead projecting from the corner edging. The sheet is stretched over the bead to elevate a central portion of the sheet from the substrate, and the sheet is peripherally secured in place.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mounting a sheet, and to arrangements where the sheet may have been artistically marked either before or after mounting. 
     2. Description of Related Art 
     As is known, a canvas stretcher is typically a wooden frame over which canvas is stretched and secured in place, before an artist begins painting. This wooden frame is built from four wooden pieces that are arranged as a rectangle and secured at their corners. Finding wooden elements that are adequately straight can be difficult. Also, the finished frame can be distorted by humidity-induced warping, which can affect the tension and flatness of the canvas. Also, the section of canvas lying directly on the frame will be rigidly supported and will not exhibit the feel or “bounce” preferred by artists. 
     Securing a canvas to such a frame requires some skill, and the results may be non-uniform when using the conventional mounting method, sometimes referred to as “gallery wrap.” In this conventional arrangement, the canvas will be stapled onto the back of one side of the frame. Thereafter, the canvas is pulled across the front, and wrapped around the opposite side of the frame, before being stapled on the back. Just before stapling, a desired tension is applied to the canvas manually, or by using pliers designed for this purpose. In some cases, wedges are tapped into the miter joints at the corners of the stretcher frame to separate the joint and increase canvas tension. Thereafter, the process is repeated for the two other sides. 
     See also U.S. Pat. Nos. 4,179,830; 5,502,906; 4,947,561; 5,133,140; 5,517,775; and 3,830,278 See also Japanese Patent Application 08-072597, filed 27 Mar. 1996; and Japanese Patent Application 2000-347327, filed 10 Oct. 2000; as well as WIPO International Publication 2008/142351, published 27 Nov. 2008. 
     SUMMARY OF THE INVENTION 
     In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a method for installing a sheet on a substrate using a corner edging with a corner bead. The method includes a number of steps, performed in any order. The method includes the step of placing the corner edging around the substrate peripherally. Another step is positioning the sheet on the bead of the corner edging. The method includes the step of stretching the sheet over the bead to elevate a central portion of the sheet from the substrate. Another step is peripherally securing the sheet in place. 
     In accordance with another aspect of the invention, a mounting system is provided. The system includes a substrate having a front and a back. The system also includes an edging and a sheet. The edging has a prominent bead and is positioned on the substrate peripherally. The sheet is positioned over the bead and is under tension to lift away from the front of the substrate. The sheet is peripherally secured in place. 
     In accordance with yet another aspect of the invention, an edging is provided for accommodating mounting of a sheet onto a substrate. The edging includes a plurality of elongated edging segments, each having a transverse pair of flanges forming an inside corner and an outside corner. Each of the plurality of edging segments has a bead. The bead projects distally away from the outside corner. 
     By employing apparatus and methods of the foregoing type, improved techniques are achieved for mounting sheets intended for artistic markings. In a disclosed embodiment, corner edgings are placed at the upper corners of a solid, high-density foam substrate, or a substrate formed of other materials. These corner edgings have two flanges that embrace the substrate&#39;s corner. The edgings also have a rounded bead that projects outwardly from the flanges. The corner edgings can be nailed in place or, in some cases, can simply rest in position waiting for subsequent operations. 
     In a disclosed embodiment, one edge of a sheet (e.g. canvas, paper, split fiber non-woven sheets, etc.) is secured to the back of the substrate with staples, adhesive tape, double-sided adhesive strips, or the like. The sheet is then routed over the corner edging on one side, across the front of the substrate, and around the corner edging on the opposite side. At this stage the sheet can be stretched manually or with pliers designed for this purpose. Thereafter, the free end of this sheet can be secured to the back of the substrate with staples, double-sided adhesive strips, adhesive tape, etc. With two sides of the sheet now secured, the installer can now repeat the process for the other two remaining sides. 
     Because the corner edging has a prominent bead, the sheet is lifted off the front of the substrate, to give the sheet the feel and bounce preferred by artists. 
     In some cases corner edging can be placed on both the upper and lower corners of the substrate. In a disclosed embodiment, the corners of the sheet can be notched to provide flaps, and these flaps are given a pair of creases to assist in installing the lower edging destined for the lower corner of the substrate. A first one of these creases is created by simply wrapping the flap around the upper edging, and then folding the flap around the lower corner of the substrate without the lower edging present. The lower edging can then be placed over the folded flap at the lower corner and used as a guide in creating a second precursor crease by folding the flap back over the lower edging. This second precursor crease is then reversed to form a final crease that becomes a pocket to hold one of the flanges of the lower edging, which is then lifted into position at the lower corner of the substrate. Because creases are first formed without allowing space for the lower edging, bringing the flap into position with the lower edging in place, produces a desirable tension in the sheet. 
     In another embodiment tension can be created by installing the sheet and corner edgings on a substrate that has been bowed. Tension is created once the bowing is released and the substrate returns to its normal flat condition. Instead of bowing, in one embodiment the substrate is formed of a pair of panels that are hinged together on the front with adhesive tape. Again, the sheet and corner edgings are installed while the substrate is articulated at the hinge joint into an oblique angle, followed by a flattening of the substrate to create tension. Another strip of adhesive is then placed at the back of the temporary hinge joint to prevent further articulation there. 
     In yet another embodiment, corner edgings are secured in advance to a sheet, using the substrate as a spacing gauge. The edgings are oriented with one of their flanges upright and pressed against opposite edges of the substrate (the substrate is acting as a spacing gauge). Their remaining flanges extend outwardly along the sheet and are eventually secured to the sheet using the spacing determined by the substrate. Thereafter, the substrate is removed and the edgings are rotated inwardly while the substrate returns and is pressed against the formerly upright, free flanges. Because of the geometry, pressing these free flanges down with the substrate intervening, causes a desirable stretching of the sheet. 
     These corner edgings can be notched or can otherwise be made flexible to follow a curvature in the substrate. In fact, these edgings can accommodate substrates that have convex or concave curvature or have interior openings (e.g. an annular substrate). 
     An advantage of using foam for the substrate is easy mounting to a wall or other surface. In a disclosed embodiment, a fastener (e.g., a screw, nail, or other fastening means) can be partially driven into a wall and remain proud. The foam of the substrate can be pressed against the protruding portion of the fastener to be impaled thereon. Thus, the substrate can be mounted without the need for hardware or specialized mortises. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein. 
         FIG. 1  is a perspective view of a sheet about to be mounted on a substrate in accordance with principles of the present invention; 
         FIG. 2  is a cross-sectional view showing the sheet of  FIG. 1  in the process of being mounted on the substrate; 
         FIG. 3  is a cross-sectional view of the arrangement of  FIG. 2  with the sheet being wrapped around a substrate to advance the mounting of the sheet; 
         FIG. 4  is a cross-sectional view of the arrangement of  FIG. 3  with the sheet secured in place; 
         FIG. 5  is a cross-sectional view of an arrangement that is an alternate to that of  FIG. 4  wherein a sheet is being stretched with pliers; 
         FIG. 6  is a cross-sectional view of an arrangement that is an alternate to those mentioned above; 
         FIG. 7  is a cross-sectional view of an arrangement that is an alternate to those mentioned above; 
         FIG. 8  is a cross-sectional view of an arrangement that is an alternate to those mentioned above, and shown about to be mounted on a wall; 
         FIG. 9  is a fragmentary, perspective view of an arrangement that is an alternate to those mentioned above; 
         FIG. 10  is a perspective view of a substrate that can be used with the apparatus of  FIG. 9 ; 
         FIG. 11  is a fragmentary, perspective view of another setup that is an alternate to that of  FIG. 1 ; 
         FIG. 12  is a fragmentary, perspective view of a layout that follows the setup of  FIG. 11 ; 
         FIG. 13  is a fragmentary, perspective view of a layout that follows the layout of  FIG. 12 ; 
         FIG. 14  is a cross-sectional, elevational view through one of the ends of the layout of  FIG. 13  after installation is completed; 
         FIG. 15  is a cross-sectional view of an arrangement that is an alternate to those mentioned above, and shown with a substrate bowed before completing the mounting of a sheet; 
         FIG. 16  is a cross-sectional view of an arrangement that is an alternate to that of  FIG. 15 ; 
         FIG. 17  is an elevational view, with portions broken away for clarity, of a setup that can be used with any of the apparatus of  FIGS. 1-6 ; 
         FIG. 18  is an elevational view of a layout that follows the setup of  FIG. 17 ; 
         FIG. 19  is an elevational view, with portions broken away for clarity, of a setup that can be used with any of the apparatus of  FIGS. 1-6 ; and 
         FIG. 20  is an elevational view of a layout that follows the layout of  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a substrate  10  is shown as two rectangular, solid panels  10 A and  10 B that are placed side-by-side and attached together to form a single, rectangular substrate with a unitary front surface. Panels  10 A and  10 B may be attached together with adhesive, by wrapping adhesive tape around their joint, by stapling, or by other fastening means. 
     In this embodiment each of these slabs  10 A and  10 B are made of high-density foam, although other types of material can be used instead. Substrate  10  is a simple rectangular solid, but in other embodiments the substrate may have a border that is polygonal or curved. Also, while substrate  10  is shown with a flat front and back, in some embodiments those surfaces may have concave features, such as a dished shape, or parallel grooves. Good results are achieved when substrate  10  has a periphery surrounding an internal region occupied by solid material. 
     Disposed around the periphery of substrate  10  are a number of separate edging segments  12 ,  14 ,  16 ,  18 A, and  18 B (also referred to as corner edging). Edging segment  12  is shown about to be mounted at an upper corner on one edge of substrate  10 . Edging segment  16  is shown about to be mounted at the opposite edge of substrate  10 . Edging segment  14  is shown about to be mounted at an upper corner of an adjacent edge of substrate  10 . A pair of aligned edging segments  18 A and  18 B are shown about to be mounted on an upper corner of substrate  10  on the substrate edge that is opposite to the edge on which edging segment  14  is to be mounted. Once installed in place, edging segments  14  and  18 A will reinforce the joint between slabs  10 A and  10 B. 
     Edging segments  12 ,  14 ,  16 ,  18 A, and  18 B have the same cross-section and the same general, elongated configuration. In fact, each of them can have originated as a single piece that is then cut into segments of the desired length. Taking edging segment  12  as an example, it has a pair of transverse flanges  12 A and  12 B, extending at right angles from a rounded, prominent bead  12 C. Flanges  12 A and  12 B form an inside and an outside corner. Bead  12 C projects outwardly (distally) from this outside corner. 
     Each end of edging segments  12 ,  14 , and  16  are mitered to provide a miter joint, although the mitered ends need not necessarily touch, but the mitering will provide clearance allowing the segments to come closer together. The adjacent ends of segments  18 A and  18 B are square cut, but their other ends are mitered to interface with segments  16  and  12 , respectively. 
     Flanges  12 A and  12 B each have an aligned series of nail holes  12 D and  12 E, respectively. These nail holes may be arranged in a fashion similar to corner beads that are used to finish drywall. In fact in some embodiments, an assembler may use the conventional corner beads normally intended for finishing drywalls. In various embodiments, corner edging  12  may be a metal stamping, plastic extrusion, a pair of plates that are welded together, etc. 
     Sheet  20  is shown above substrate  10  prior to installation. Sheet  20  has a rectangular outline but with notches  22 A,  22 B,  22 C, and  22 D that effectively produce folding flaps  20 A,  20 B,  20 C, and  20 D, which surround the central portion of the sheet. Notches  22 A- 22 D align with the four upper corners of substrate  10 . 
     As described further hereinafter, sheet  20  is intended to receive artistic manual markings made with paint, watercolors, charcoals, etc. Accordingly, sheet  20  may be canvas, paper, sheet metal, a plastic membrane, etc. Good results are achieved with split fiber, non-woven sheets, which have a smooth surface, archival quality, excellent stability with changing temperature and humidity, and accommodate a wide variety of marking/painting techniques. 
     Installation of sheet  20  begins by placing edging segments  12 ,  14 ,  16 ,  18 A, and  18 B at the indicated upper corners of substrate  10 . Thereafter sheet  20  is laid on top and flap  20 C (choice of starting flap is arbitrary) is wrapped around edging segment  16  and secured to the back of substrate  10  with glue, adhesive tape, staples, or other fastening means. Thereafter the installer will work with flap  20 A. 
     Referring to  FIG. 2 , an installer in a shown grasping and pulling an end of flap  20 A with fingers F. This creates tension across the central portion of sheet  20 . The installer will adjust the magnitude and distribution of the tension to remove wrinkles from sheet  20 . Double-sided adhesive strip  24  has been installed on the back of substrate  10 , reaching from the lower corner inwardly a predetermined amount, and laterally extending across the associated side of substrate  20 . 
     Referring to  FIG. 3 , flap  20 A has been wrapped around the lower corner of substrate  10 , while the installer maintains even and constant tension in sheet  20 . The installer completes this step by pressing flap  20 A onto double-sided adhesive strip  24 , to secure the flap in place. 
     The foregoing process that enveloped corner edging  12  and  16  will now be repeated with corner edgings  14 ,  18 A, and  18 B ( FIG. 1 ). For example, flap  20 B may be folded around corner edging  14  and secured to the back of substrate  10  before wrapping flap  20 D around corner edgings  18 A and  18 B and securing flap  20 D in the manner illustrated in  FIGS. 2 and 3 . 
     In  FIGS. 2 and 3 , sheet  20  is shown elevated above substrate  10  to leave underlying space  27 . This elevation is achieved because bead  12 C is prominent and projects distally from the outside corner formed by flanges  12 A and  12 B. These Figures show that bead  12 C is hollow and is shaped much like three-quarters of a hollow cylinder. In other embodiments, the bead can be solid and may have a cross-section that is oval or polygonal. Good results are achieved when the outside of bead  12 C is smooth, which makes pulling sheet  20  over the bead easier. 
     Referring to  FIG. 4 , flap  20 A is shown secured onto double-sided adhesive strip  24  at a location on sheet  20  distal from corner edging  12 . Additional security is achieved by taping adhesive tape  26  so it reaches from a peripheral position on flap  20 A inwardly to an interior position on the back of substrate  10 . Tape  26  may be one long strip running parallel to the edge of flap  20 A, or may be a number of shorter segments that run transversely across spaced positions on the flap and onto the back of substrate  10 . 
     In any event, sheet  20  is now ready for artistic marking with paint, watercolors, charcoal, or with other artistic marking techniques. 
     Referring to  FIG. 5 , sheet  20  is wrapped around corner edging  12  and the lower corner of substrate  10 , as shown previously in  FIG. 3 . Unlike  FIG. 3 , this Figure shows a pulling force being applied to flap  20 A by the jaws  28 A and  28 B of pliers  28 . Next to jaw  28 B are a series of sharp ridges  28 C that take traction on and roll across the back of substrate  10  as an installer leverages pliers  28  to adjust tension. Once the desired tension is achieved, the installer can hold flap  20 A in place, release pliers  28 , and secure the flap in place with staples (not shown). It will be noticed that in  FIG. 5  the installer does not use the double-sided adhesive strip shown previously (strip  24  of  FIG. 2 ). 
     Referring to  FIG. 6 , previously mentioned substrate  10  is fitted again with corner edging  12 , shown with its flange  12 A on the periphery, and flange  12 B on the front. In this embodiment flanges  12 A and  12 B are each secured with a series of nails. Specifically nails N 1  and N 2  are driven through flanges  12 A and  12 B, respectively. These nails are secured through pre-existing nail holes (see nail holes  12 D and  12 E of  FIG. 1 ). As before, the end of flap  20 A is secured by adhesive tape  26 , but without using a double-sided adhesive strip (i.e., without strip  24  of  FIG. 4 ). 
     Referring to  FIG. 7 , previously mentioned substrate  10  is fitted again with corner edging  12 , shown with its flange  12 A on the periphery, and flange  12 B on the front. The lower corner of substrate  10  has been fitted with another corner edging  112 , having its flange  112 A on the periphery, and its other flange  112 B on the back. Sheet  20  conveniently holds corner edging  12  in position during assembly, but corner edging  112  has a tendency to stray when manipulating sheet  20 . For this reason, double-sided adhesive strip  124  has been placed on the back of substrate  24  to hold corner edging  112  in place. Also, double-sided strip  124  extends beyond flange  112 B and this extension is used to secure flap  20 A to the back of substrate  10 . For additional security, adhesive tape  126  is taped over the edge of flap  20 A and onto the back of substrate  10 . 
     Referring to  FIG. 8 , sheet  20  has been installed around corner edging  12  and secured in place with double-sided adhesive strip  24  as shown in  FIG. 4 . Unlike  FIG. 4 , additional security is provided by staple ST, eliminating the need for the adhesive tape (tape  26  of  FIG. 4 ). Specifically, staple ST is driven through flap  20 A and into the back of substrate  10 . 
     In this embodiment, a fastener N 3  (e.g., a nail, screw, or other fastener) has been partially driven into wall W so the fastener stands proud. Substrate  10  is pressed firmly against the head of fastener N 3  impaling the foam of the substrate on the fastener. Accordingly, sheet  20  can be quickly hung for display without the need for special hardware or for mortises at substrate  10 . 
     Referring to  FIGS. 9 and 10 , corner edging  212  is similar to edging  12  of  FIG. 1 , and corresponding components have the same reference numerals, but increased by 200. In this embodiment, flange  212 B has a number of spaced notches  212 F that allows an installer to bend corner edging  212 , in this case to create a curvature that matches the curvature of substrate  210 . Substrate  210  is again a high density foam, the same as the foams used in the other substrate (i.e., substrate  10  of  FIG. 1 ). 
     Substrate  210  can have an arbitrary shape such as the annular shape shown in  FIG. 10 . Annular substrate  210  has a convex outside edge, as well as a concave inside edge that defines an inside opening  210 C. Corner edging  212  can be installed at the inside opening  210 C, but the installer must bend the edging in reverse to match the concave curvature of opening  210 C. 
     Referring to  FIG. 11 , corner edging  312  is similar to the edging previously illustrated, but has been sharply bent 90° to wrap around two adjacent edges of substrate  10  (substrate  10  being illustrated with its back facing up). Such a sharp bend can be achieved by notching a flange as shown in  FIG. 9 , but in this case cutting a larger, 90° notch. In this embodiment the 90° notch is made in the flange of edging  312  that is hidden in this view against the front of substrate  10 . Slit  330  is cut in the other, transverse flange to divide that flange into flange sections  312 A and  312 A′. 
     In this embodiment the four lower corners of substrate  10  will be fitted with lower edgings, two of them shown herein as edgings  412  and  512 . Edging  412  ( 512 ) has a bead  412 C ( 512 C) between flange  412 A ( 512 A) and flange  412 B ( 512 B). The adjacent ends of flanges  412 B and  512 B are mitered (beveled) to provide mutual clearance when they reach their ultimate destination at the back of substrate  10 , as will be described presently. 
     Sheet  120  has four flaps, flaps  120 A and  120 B being visible in this Figure. Flap  120 A is shown with two creases  132  and  134 . Crease  132  is formed by temporarily removing edging  412  and wrapping flap  120 A around bead  312 C and substrate corner  110 D (i.e., crease  132  is created by folding flap  120 A around corner  110 D). 
     With the end of flap  120 A now lying flat against the back of substrate  10 , the inside corner of edging  412  is placed around crease  132  at corner  110 D with flange  412 B pressing flap  120 A down against the back of substrate  10 . Next, a precursor to crease  134  is formed by folding flap  120 A up, using the distal edge of flange  412 B as a folding guide. The fold just created is now reversed by removing edging  412  and refolding the crease in the opposite direction to finalize crease  134 . 
     The same creasing process was performed on flap  120 B to produce corresponding creases  132 ′ and  134 ′. The fold in crease  134 ′ has created a pocket for flange  512 B of edging  512 . It will be noticed that the side of flap  120 B has been trimmed to match to beveling in the end of flange  512 B. As shown for flap  120 A, the beveling does not extend beyond the edging  412  and the outlying section of the flap has been squared off. 
     Also, a rectangular region  134  has been left between the edgings  412  and  512 , near the corner distinguished by slit  330 . Rectangular region  134  has fold lines  134 A,  134 B, and  134 C whose purpose will be described presently. 
     It will be appreciated that crease  132 ′ was created with edging  512  absent. However, now that edging  512  is in place as shown, crease  132 ′ is ostensibly not far out enough to allow crease  312 ′ to simultaneously reach around the now-present edging  512  and arrive at corner  110 E. This means that the installer must apply tension by pulling on flap  120 B and edging  512 , in order to bring the inside corner of edging  512  up to the substrate corner  110 E (It will be understood that the flap opposite to flap  120 B is resisting this tension, in a manner that will be described presently.) 
     Referring to  FIGS. 12 and 13 , corner edging  512  has been pulled up so that its inside corner embraces corner  110 E. 
     As with flap  120 B, flap  120 A will be a folded around the distal edge of flange  412 B, before applying tension to the flap and edging in order to bring the inside corner of edging  412  onto substrate corner  110 D. 
     As shown in  FIG. 13 , when pulling flap  120 A into position, rectangular region  134  will be tucked inwardly by folding it as shown along fold lines  134 A,  134 B, and  134 C. This will produce a clean seam without any extraneous sheet material visible. 
     Referring to  FIG. 14 , edging  412  is shown in its final position. Flange  412 B is shown up against the back of substrate  10  with a section of flap  120 A intervening between the flange and the substrate. Flange  412 A is shown facing the edge of substrate  10  with flange  312 A intervening between the substrate and flange  412 A. To keep the assembly in place reliably, adhesive tape  226  has been laid down, reaching from the back of substrate  10  to a portion of flap  120 A overlying flange  412 B. 
     As was previously mentioned, tension applied to flap  120 A and flap  120 B is resisted by tension in flaps (not shown) on the opposite side. This resistance is created by securing that opposite flap using the method just described for flap  120 B (although one of the other methods described above can be used instead). The securing of these two opposing flaps can be performed in succession. Alternatively, both flaps can be prepared by creating for both the conditions shown for flap  120 B of  FIG. 11 , and then simultaneously lifting both flaps to achieve the orientation shown in  FIG. 12  for flap  120 B. 
     Referring to  FIG. 15 , substrate  610  may be a high-density foam, similar to that previously described, although in this embodiment good results are achieved if the substrate is not made from two slabs (e.g., slabs  10 A and  10 B of  FIG. 1 ). The assembly method proceeds by first taping one end of previously mentioned sheet  20  to the back of substrate  610 , near its periphery. Next, substrate  610  is temporarily bowed by hand so its front becomes concave, bringing its two front corners closer together. Thereafter, the opposite edge of sheet  20  is taped to the back of substrate  610  while it is still bowed. 
     The inside corner of previously mentioned corner edgings  12  and  16  may be placed on the front corners of substrate  610  at this time, although in some cases one may pre-position the edgings and, optionally, hold them in place with adhesive tape, nails, or other fastening means. 
     Substrate  610  may now be released to end the bowing and allow the substrate to return to its normal flat condition. This release causes the front corners of substrate  610  to spring back and apply tension to sheet  20  to create a condition similar to that shown in  FIG. 6 . 
     Referring to  FIG. 16 , substrate  710  is made of two equally-sized solid panels  710 A and  710 B of high-density foam, or other materials. Panels  710 A and  710 B are hinged together with a strip of adhesive tape  736 . Tape  736  is positioned so that panels  710 A and  710 B can be swung into an abutting position, although in this Figure they are shown hinged apart leaving an opening in the back. Accordingly, the distal front corners of panels  710 A and  710 B are closer together than they would be if lying flat. 
     Next, opposite edges of sheet  20  are taped with adhesive tape  26  to the back of panels  710 A and  710 B near their distal edges. Corner edgings  12  and  16  may be placed at the front corners of panels  710 A and  710 B, either before or after the taping of sheet  20 . 
     Substrate  710  is now pressed to bring the joint between panels  710 A and  710 B close to the central portion of sheet  20 . Eventually, the panels  710 A and  710 B are abutting and coplanar and substrate  710  is flat. Once this condition is achieved, the assembler then applies adhesive tape  738  across the back of the joint between panels  710 A and  710 B. Since panels  710 A and  710 B are taped in front and back, they no longer have a free hinge joint and substrate  710  functions as a single entity. 
     The flattening of substrate  710  causes the front corners of the substrate to move apart and apply tension to sheet  20  to create a condition similar to that shown in  FIG. 6 . 
     Referring to  FIG. 17 , sheet  20  is laid flat and previously mentioned corner edgings  12  and  16  are secured to the sheet with double-sided adhesive strips  40 . Before being secured by adhesive strips  40 , the spacing between the opposing pair of separate corner edgings segments  12  and  16  is established by using opposite edges of substrate  10  as a gauge. 
     Specifically, the unsecured, free flanges  12 B and  16 B are placed flat against substrate  10 , with the substrate elevated above the beads  12 C and  16 C, and adjacent flanges  12 A and  16 A oriented to project outwardly along sheet  20 . Once in the correct position, adjacent flanges  12 A and  16 A are then secured onto strips  40 . Note that now, if one were to try to push substrate  10  down, the substrate would need to push beads  12 C and  16 C away, thereby placing sheet  20  under tension. 
     Instead, substrate  10  is now removed and the assembler rotates edging segments  12  and  16  as shown in  FIG. 18  to bring free flanges  12 B and  16 B closer to sheet  20 . At the same time substrate  10  is pressed downwardly to bring it flat against flanges  12 B and  16 B. This completes the rotation of edgings  12  and  16 , and brings flanges  12 A and  16 A flat against the edges of the substrate  10 . 
     It will be noticed that during this operation, beads  12 C and  16 C rolled inwardly across sheet  20 , thereby making the clearance for substrate  10  between flanges  12 A and  16 A even tighter. Accordingly, the foregoing operation produces tension in the central portion of sheet  20 , without the need for special manipulation or special tools. 
     Finally, the distal ends of sheet  20  can be trimmed to be coterminous with flanges  12 A and  16 A, or can be folded around the back of substrate  10  and taped down as shown in  FIG. 6 . 
     Referring to  FIG. 19 , this setup is the same as was shown for  FIG. 17 , except that a relatively thin substrate  810  is used in this embodiment. Substrate  810  can be a thin panel of metal, plastic, wood, plywood, etc. As before, substrate  810  is used as a gauge to set the spacing between flanges  12 B and  16 B before securing flanges  12 A and  16 A on sheet  20  with double-sided adhesive strip  40 . 
     Referring to  FIG. 20 , substrate  810  is shown being pressed downwardly to lie flat against flanges  12 B and  16 B. Again, the rotation of corner edging segments  12  and  16  applies tension in the central portion of sheet  20 . The distal ends of sheet  20  can be trimmed to be coterminous with flanges  12 A and  16 A, or can be folded around those flanges. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.