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SPECIFIC DATA RELATED TO INVENTION 
   This application claims the benefit of U.S. Provisional Application No. 60/764,204 filed Feb. 1, 2006. 
   The present invention relates to fences and more particularly to fence rails and protective covers for use with such rails. 

   BACKGROUND OF THE INVENTION 
   Picket fences are conventionally constructed with horizontally extending rails that may be attached at each end to a vertically extending post or an edge of a building. Pickets are attached to and supported by the rails with the pickets extending generally vertically to the rails. The pickets may be attached to the rails by means of fasteners, such as screws, extending through a respective one of the rails and into a corresponding one of the pickets. One of the issues that arise with use of such fasteners to attach rail to picket is that the fastener is exposed and generally unsightly. Further, the fastener is subject to corrosion from exposure and may become even more unsightly and, in addition, such corrosion may result in streaks or discoloration at the attachment sight. Accordingly, it would be desirable to provide a method and system for picket to rail attachment that reduces the undesirable appearance of exposed fasteners. 
   SUMMARY OF THE INVENTION 
   A method and apparatus for concealing and protecting fasteners used in the attachment of rails to pickets in a picket fence utilizes a rail formed with a lengthwise extending slot having a base for contacting a picket. The slot is sized and configured to receive a snap fit cover that closes the slot and protects the slot from weather while providing an outer surface to hide the slot and any fasteners in the slot. In use, the pickets are attached to the rail by screws or other suitable fasteners that project through the base of the slot and into the associated pickets to securely attach the pickets to the rail. Once the pickets are all attached to the rail, the cover is positioned adjacent the slot and can be pressed into the slot to conceal the fasteners. The slot is preferrably formed with a pair of flanges extending along the lengthwise direction of the rail and located within the slot. One flange is along a top side of the slot and the other flange is along a bottom side of the slot. The cover is formed with a pair of mating flanges so that the cover can be pressed into the slot and the mating flanges interact to fasten the cover in place. The shape and arrangement of the flanges is such that the cover forms a tight fit within the slot to minimize water intrusion. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     For a better understanding of the present invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings in which: 
       FIG. 1  illustrates one form of conventional picket fence structure with which the present invention may be used; 
       FIG. 2  is a cross-sectional view of one form of rail according to the teaching of the present invention and an associated picket; 
       FIG. 2A  is an enlarged cross-sectional view of a rail assembly in one form of the present invention; 
       FIG. 3  is a cross-sectional view of another form of rail according to the teaching of the present invention and an associated picket; 
       FIG. 4  is a cross-sectional view of a rail insert or cover that can be attached to the rails of  FIGS. 2 and 3  to conceal rail-to-picket fasteners; and 
       FIG. 5  is a cross-sectional view of a rail and cover in association with a picket. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is an elevation view of one type of fence with which the present invention may be used. The fence  10  comprises a plurality of vertically extending members or pickets  12  which may have a rectangular cross section and a plurality of rails  14  (inclusive of rails  14 A,  14 B and  14 C) that are used to fix the position of each of the members  12 . The rails  14  and members  12  are typically formed of aluminum and attached at each intersection by a screw passing through the rail  14  and threadedly engaging the member  12 . One of the issues with this type of fence construction is that the heads of the screws are visible and generally detract from the ornamental effect of the fence. Additionally, the screws provide a site for moisture and other debris to accumulate and can produce corrosion since the screws are made from metal. While most such fences are aluminum, it is also known to construct such fences from various synthetics polymers and to attach the rails and pickets with fasteners such as screws, bolts and rivets. 
   It should be noted that the top rail  14   a  is adapted to fit over the top end of some pickets or members  12  while the middle rail  14   b  fits over the ends of some members  12  and attaches to the side of other members  12 . Rail  14   c  is adapted to attach with side mounting to all of the members  12 . Accordingly, different configurations of rails are required to permit such disparate attachment. 
     FIG. 2  is a cross sectional drawing of one form of rail  14 A particularly design as a top rail for use with the members  12  which incorporates a slot  18  for seating attachment screws  20  below the upper or outermost surface  16  of the top rail. The rail  14 A has an L-shaped segment  17  that forms, in conjunction with front rail portion  19 , a U-shaped opening  24  for snugly receiving the top of the members  12 . The overlapping L-shaped segment provides a smooth top rail surface. The screws  20  thread into the top of each member  12  to attach the rail to the member. The slot  18  is defined by a pair of opposite side walls  21 A and  21 B and a generally flat base  21 C. Each side wall  21 A,  21 B incorporates a lengthwise extending flange  26 A,  26 B spaced from the base  21 C so as to define a respective channel  22 A,  22 B between each flange and the base.  FIG. 3  illustrates a rail  14  without the L-shaped segment  17  that may be used as an intermediate rail below the top rail  14 A or may be used in those cases in which it is desired to have the pickets protrude above the top rail. 
     FIG. 4  is a cross sectional drawing of a cover  30  for use with the rail  14 . The cover  30  comprises a formed strip having a flat plate portion  32  and a pair of lengthwise extending leg members  34   a  and  34   b  depending generally perpendicularly from the portion  32 . Each of the members  34   a ,  34   b  are formed with outwardly extending flanges  36   a  and  36   b  adjacent their respective ends. The flanges  36   a ,  36   b  are sized to fit into corresponding ones of the channels  22 A,  22 B of the slot  18  of rails  14 . The length of each of the leg members  34  is such as to cause the portion  32  of the cover  30  to seat flush within the slot  18  so as to present a generally continuous flat outer surface of the rail  14  and cover  30  assembly as shown in  FIG. 5 . The edge surfaces  38   a ,  38   b  of the plate portion  32  abut against the flanges  26   a ,  26   b  to establish a seating depth for the cover while the edges  42   a ,  42   b  seat against the shoulders  40   a ,  40   b  of rail  14  to establish the flush outer appearance. 
   It will be noted from the drawings that the flanges  26   a ,  26   b  are each shaped with an inwardly sloped forward surface for causing the flanges  36   a ,  36   b  to ride up onto and over the flanges  26   a ,  26   b  as the cover  30  is pressed into slot  18 . The legs  34   a ,  34   b  of the cover are designed with sufficient elasticity to allow this deflection of the legs and then to spring back to their original shape as the flanges  36   a ,  36   b  pass by the flanges  26   a ,  26   b . The shape of the flanges  36   a ,  36   b  is essentially a reverse of the shape of the flanges  26   a ,  26   b  so that the sloped portions of both sets of flanges are effective to cause the legs  34   a ,  34   b  to deflect inwardly. The back edge of each set of flanges  26   a ,  26   b  and  36   a ,  36   b  are formed with a more abrupt surface to establish a locking relationship between the fully inserted cover and the rail. 
   As best seen in  FIG. 5 , the relationship in size of the rail  14  and cover  30  is such as to define a snug fit of the cover within the slot  18  and preferrably to establish proximal contact between the cover  30  and the screws  20 , particularly if the screws  20  start to loosen. This provides the added benefit of locking the screws into the assembly to prevent loosening while hiding the screws from view. Further, the snug fit between the edges  40  and  42  provides some degree of moisture barrier. It will also be noted that the cover could be extruded as a plastic material while the rail could be formed of aluminum. The cover  30  could be a different color from that of the rail  16  thereby creating an accent strip. The cover  30  may also hide any blemishes on the rail  16  caused by insertion of the screws  20  if overtightened or inserted incorrectly or if the rail is scratched by a slipped screwdriver. 
   While the embodiments of the rail  14  illustrated in  FIGS. 2 and 5  include a U-shaped top for receiving the ends of the pickets  12 , it will be recognized that the extruded rail indicated at  14   c  in  FIG. 1  would not require a U-shaped top. Accordingly, the rail  14   c  could be extruded in a form such as that shown in  FIG. 3  or in some other more eye-appealing configuration. Further, while the slot and cover have been shown in what is considered to be a preferred embodiment, it will be apparent that other shaped slots and covers could be developed within the scope of the present invention. It is intended therefore that the invention not be limited to the specifically disclosed configuration but that it be interpreted within the full spirit and scope of the appended claims.

Summary:
A fence rail assembly is provided comprising an extruded rail having a lengthwise extending slot for receiving a plurality of fasteners for attaching the rail to a plurality of pickets. The slot is designed with internal flanges adapted for engaging mating flanges on legs of a cover to be placed on the slot. The cover is sized to fit snugly at the slot opening to minimize water and debris intrusion, as well as prevent loosening of the fasteners.