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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to siding panels and more particularly, a siding panel having a latched nail hem for securing the siding to a structure. 
     2. Description of the Related Art 
     Vinyl or metal siding is increasingly used as a convenient and relatively inexpensive covering for residential and commercial buildings. Generally, siding is formed with a nailing strip, or single-ply nail hem, having preformed apertures for accepting a mounting nail or the like at the top of each section of siding to fasten the siding to the structure. A problem with the use of a single-ply nailing strip is that during the manufacture of the siding, edge portions of the siding tend to thin by tapering downwardly. Over time, repeated exposure to wind load may cause the mounting nail to tear through this thin portion of siding at the aperture, resulting in damage to the siding and, possibly, to the structure. Further, this thinning of the siding at the single-ply nail strip may also cause the aperture to weaken and thus stretch, which results in the siding pulling out over the mounting nail. 
     Another concern with single-ply nail hems is problems resulting form improper installation. Specifically, installing the mounting nails such that the nails are tight against the siding causes the siding panel to buckle with changes in temperature. 
     In an effort to remedy this problem, siding has been formed with a double-ply nail strip, i.e. a nail hem, by folding the nailing strip over on itself, as shown in FIG. 1, and ending in a free end. In the more effective double-ply nail hems, the free end extends downwardly a considerable extent and apertures are provided in both plies of the nail hem. As the siding is mounted to the structure, the fasteners extend through both nail plies. The double-ply nail hem is formed such that each ply is separated by a small span, and the fasteners, when properly installed, are not completely sunk, thus maintaining the span gap between the two plies of the nail hem. The siding is thereby allowed to glide the span between the two plies of the nail hem to compensate for the effect of wind, without the siding tearing through the fasteners. 
     The double-ply nail hem offers a dramatic increase in wind-load resistance. However, the concern of tight nailing still exists, which affects the panels ability to expand and contract. Further, the curl of the nail hem is susceptible to stress relaxation, which causes the outer ply to move outwardly and exert pressure against the fasteners and hindering the proper expansion and contraction of the panel. Further, there is limited control for the curl spacing during manufacture. The imprecise control over the span between the laminae lessens its effectiveness to withstand wind load and more specifically lessens the panel&#39;s ability to expand and contract due to temperature changes. 
     Thus, a need exists for a siding panel having a nail hem that is effective against stress relaxation and improper placement of fasteners. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a siding panel that withstands the stresses due to stress relaxation. It is further an object of the present invention to provide a siding panel that withstands extreme wind load applications, without comprising the panels ability to expand and contract in reaction to temperature change. 
     The siding panel of the present invention solves the problems identified in the related art. The siding panel hereof is preferably formed as an elongated panel having a front side and a rear side. The siding panel comprises a nail hem for securing the siding panel to a support structure. The nail hem includes a proximal laminae for mounting adjacent to the support structure and a distal laminae spaced from the proximal laminae and the support structure. The distal laminae terminates in a free end. The siding panel further includes a catch projecting outwardly from the panel. The catch serves as an impediment for the free end of the distal laminae thereby preventing further outward movement of the free end of the distal laminae 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiment of the present invention is further described in connection with the accompanying drawings, in which: 
     FIG. 1 is a side elevational view of a prior art version of a nail hem; 
     FIG. 2 is a perspective view of the side panel in accordance with the present invention; and 
     FIG. 3 is a cross-section taken along line  3 - 3  of FIG. 2 showing the latched double-ply nail hem of the present invention; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiment of the present invention, an example of which is illustrated in the accompanying figures. Whenever possible, the same reference numbers will be used throughout the description and figures to refer to the same or like parts. 
     Referring now to the drawings, a siding panel  10  in accordance with the present invention is preferably manufactured as a single elongated article from a unitary sheet of synthetic resin such as polyvinyl chloride. As shown in FIG. 2, the panel presents a front side  12 , which may be embossed with a pattern such as simulated wood grain, and a back side  14 , which typically lacks such embossing and is meant to be mounted adjacent to the structure. Broadly, the panel presents a double-ply nail hem  16 , a receiver  18 , at least one stretch  20 , and a base  24  having a projection  26 . The panel  10  hereof is described in its typical generally horizontal orientation as shown in FIG. 2, but may also be oriented vertically or at other angles as desired. 
     The double-ply nail hem  16  is positioned uppermost on the panel  10  and includes a proximal member  28 , a distal member  30  and a curl  32 . As the panel  10  is mounted to the structure, the proximal member  28  abuts the structure and includes a substantially flat span extending downwardly from the curl  32  of the nail hem. The proximal member  28  includes a plurality of perforations, which typically are horizontally elongate to permit expansion and contraction along the length of panel  10  due to temperature changes. 
     The distal member  30  of the double-ply nail hem likewise includes a substantially flat span extending downwardly from the curl  32  and terminates in a free edge  34 . It is to be understood that the free end of the distal member may include a bead or other formation thereon. As the panel  10  is mounted to the structure, distal member  30  is spaced forwardly away from the proximal member  28  and the structure to provide a span  31  between the proximal and distal members of the double-ply nail hem. Distal member  30  likewise further includes a plurality of perforations axially aligned with the perforation of the proximal member  28 . Distal member  30  is formed by folding an elongate nailing strip over on itself, as shown in FIG.  2 . Curl  32  thus transitions from the proximal member to the distal member at the uppermost portion of panel  10 . 
     A receiver  18  is integrally formed in the panel  10  immediately below the nail hem to allow adjacent panels to overlap thereby aiding in shedding precipitation. The receiver  18  comprises an interlock  36  projecting outwardly from the panel  10  as mounted on the structure, and curving back upon itself to form an interlock space  38  for receiving the projection  26  of an adjacent panel. The interlock  36  is formed with a first interlock flange  44 , which projects generally toward the panel  10  at a lower portion of the interlock and, in a preferred embodiment, further includes a second interlock flange  46  formed at an upper portion of the interlock. Second interlock flange  46  projects slightly toward the panel and preferably extends the longitudinal length of the panel  10 . 
     A first stretch  20  continues downwardly toward the base  24 . Preferably, a second stretch  48  is positioned below the first stretch and is staggered below the first stretch  20  by a lap  50 . Stretches  20  and  22  are shown in a conventional straight clapboard presentation, but may be provided in other well-known presentations such as Dutch lap or ship lap styles. It is to be understood that a single lap or multi-lap style may be used without departing from the scope of the present invention. 
     Base  24  is positioned at the lowermost portion of panel  10  and is configured to present a similar appearance to lap  50  as adjacent panels are interlocked and viewed from front side  12 . Base  24  includes an elbow  52  and a rearwardly projecting base leg  54 . Crook-shaped projection  26  extends upwardly toward nail hem  16  from the base at the rear portion of base leg  54 . The projection  26  is operably configured to be complemental with the receiver to permit interlocking of overlapping panels. For such purpose, the crook-shaped projection is accepted into interlock space  38  of the receiver  18  to lock the adjacent panels in proper relation. 
     In the preferred embodiment, the double-ply nail hem  16  is formed such that free edge  34  of distal member extends to receiver  18  and curl  32  presents a hair pin bend to angle the distal member back toward proximal member, as shown in FIG.  3 . As such, free edge  34  bears against the second interlock flange  46 , which interferes with the curls tendency to move the distal member outwardly due to thermal expansion or stress relaxation. The interference fit is provided by the second interlock flange  46 , which catches at least the free edge of the distal member and thus prevents its movement outwardly. It is to be understood that other interference may be provided on the panel without departing from the scope of the present invention. 
     In an alternative embodiment, free edge  34  of the distal member  30  may be secured by adhesive or other chemical fastener at its terminating edge against the proximal member  28 . As such, free edge  34  is adjoined to the proximal member thereby preventing the tendency of the curl to move the distal member outwardly due to thermal expansion or stress relaxation. In a second alternative embodiment, the free edge  34  is mechanically fastened, such as through the use of a rivet, at several distinct locations along the length of the siding panel to the proximal member thereby interfering with the curls tendency to move the distal member outwardly due to thermal expansion or stress relaxation. 
     The nail hem is preferably formed such that the span  31  between the proximal member  28  and distal member  30  is approximately 1 mm or. 0.040 in. between the respective apertures of each member. It is to be understood that other spacing may be provided without departing from the scope of the present invention. 
     In operation, the panel  10  is provided with a latched double-ply nail hem  16 , as described hereinbefore. Adjacent panels are fully locked along the length of the bottom by inserting the crook-shaped projection  26  into the interlock space  38  provided in the interlock  36 . The panel is mounted to the structure by driving a mounting nail through respective apertures of each distal and proximal member. The mounting nail should not compress the respective members of the nail hem. The mounting nails should be centered in the respective apertures to provide for the thermal expansion of the panel. Proper installation of the mounting nails provide a span  31  for outward movement of panel  10  due to wind load or stress relaxation. Further, second interlock flange maintains free edge  34  of distal member  30  within the second interlock space to prevent the stress relaxation of the curl from loosening the fasteners. 
     While preferred embodiments of the invention have been shown and described, it will be apparent to those skilled in this art that various modification may be made in these embodiments without departing from the spirit of the present invention. For that reason, the scope of the invention is set forth in the following claims:

Summary:
A siding panel is provided having a front side and a rear side. The siding panel includes a nail hem for securing the siding panel to a support structure. The nail hem has a proximal member for mounting adjacent to the supports structure and a distal member spaced from the proximal member and the support structure. The distal member terminates in a free end. The siding panel further includes a catch projecting outwardly from the panel. The catch forming an impediment for the free end of the distal member thereby preventing further outward movement of the free end of the distal member.