You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND  
       [0001]     This invention relates to a fencing system, and more particularly to a two-piece rail system, which can be incorporated into a picket fence. A picket fence comprising a pair of spaced apart parallel rails, supported by horizontal posts, and having a plurality of pickets incorporated between the rails.  
         [0002]     Picket fences are found in a variety of uses and construction types. Picket fences made of metal or plastic have a number of performance features, which make them especially desirable, including low maintenance, durability, and aesthetics. Typically the pickets of the fence are adhered to rails running nearly parallel to the ground via welding (metal) or other post attachment technique. This invention details a two-piece rail for a picket fence, and a construction method for this fence system, which can easily be constructed at a construction site. The pickets of the fence are incorporated into the system without the need for welding, or other attachment hardware and can be done by a professional or homeowner. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:  
         [0004]      FIG. 1  shows a cross sectional view of the two pieces of the two-piece fence rail  
         [0005]      FIG. 2  shows a longitudinal view of one piece of the two-piece rail  
         [0006]      FIG. 3  shows the incorporation of a picket into the two-piece rail  
         [0007]      FIG. 4  shows a diagram of the assembled two-piece fence rail incorporated into a picket fence  
     
    
     DETAILED DESCRIPTION  
       [0008]     Referring now to the figures, and in particular to  FIG. 1 , there is shown an enlarged cross-sectional view of the two pieces  100  and  200  of the two part fence rail. In a preferred embodiment, the second piece  200  of the two part rail is fabricated identical to the initial piece  100 . Piece  100  and piece  200  of the two part rail are fabricated in such a manner that first piece  100  and second piece  200  can be interlocked to form rail  300  also shown in  FIG. 1 . Utilization of a two part rail in which pieces  100 / 200  are identical, allows for a reduction in cost and ease of construction. These cost reductions include extrusion tooling, manufacturing costs, and inventory carrying costs.  
         [0009]     Again referring to  FIG. 1 , the key design features of the individual rail pieces  100 / 200  can be seen. The terminal edges  110 / 120  and  210 / 220  of the cross section of the fence rail component  100 / 200  are designed such that the individual edges will interlock with their opposing edge from another rail component. That is terminal edge  110  will interlock with terminal edge  220 ; and conversely terminal edge  120  will interlock with terminal edge  210 . The terminal edges  110 / 120  and  210 / 220  typically include a thickened bead of extruded material, to facilitate the rail-rail interlock of the two rail components  100 / 200  and to provide rigidity in the length direction of the component. Protrusions  130 / 230  are positioned on the components  100 / 200  such that they will facilitate the interlocking of the terminal edges and reduce the ability of the interlocked edges to move and or unfasten. Additionally a screw boss component  150 / 250  is included to allow for the rail to be affixed to a terminal fence post and to allow for seating of a fence picket into the rail system.  
         [0010]     In one embodiment, the two part rail is made from extruded aluminum. Other material which may be used include extruded thermoplastic polymers. Typically the materials used for the two part rail will also be used in the production of the other components of the fence system.  
         [0011]     Now referring to  FIG. 2 , there is shown a longitudinal view of piece  100  of the two part rail. Incorporated into the rail section  100  at regular intervals are picket cutouts  101 . These cutouts are typically spaced regularly along the rail at standard intervals for pickets in a picket fence system (i.e.  4  inches). The dimensions of the cutout  101  are such that they will allow a specifically sized picket  400  to be incorporated through the rail, while not affecting the dimensional stability of the rail  300  or the individual components  100 / 200 .  
         [0012]     The incorporation of picket  400  into the cutout  101  of the rail section  100  is aided by dimples and/or tabs  401  in the picket  400 . These dimples/tabs  401  allow the picket  400  to be seated into the screw boss  150  of the rail section  100 . Additionally the seating of these dimples/tabs  401  in the screw boss  150  secure the picket into the completed rail  300  in such a manner that the picket  400  is secured.  
         [0013]     The dimples/tabs  401  are placed on the picket  400  at a distance from the terminal ends of the picket  400  that allow for the two part rail to be incorporated into the picket fence system at whichever height fits the design requirements of the fence system. In a typical fence system, two rails  300  are incorporated into the fence system. It can be seen that in the invention described, any number of rails  300  could be incorporated into the fence, only requiring the appropriate number of matching dimple/tab pairs  401  be incorporated in the pickets  400 .  
         [0014]     Referring now to  FIG. 3 , there is shown the incorporation of a picket  400  in an assembled two piece rail  300 . It can be seen that the tabs  401  project out from the picket  400  and lodge in the two screw-boss&#39;  150 / 250  of the rail  300 . The seating of these tabs  401  in the two screw-boss&#39;  150 / 250  of the rail  300  secure the picket  400  in the rail  300 . By securing the picket  400  to the rail  300  using this method, external hardware such as screws can be eliminated for securing the picket. This enhances the ease of assembly and aesthetics of the fence.  
         [0015]     Referring now to  FIG. 4 , the incorporation of the two part rail  300  and the pickets  400  into a fence section  500  can be seen. The two part rail  300 , and the pickets  400  to be incorporated therein, are designed such that multiple sections of the fence system can be easily assembled with minimal tools required at the job site. The length of the rail components  100 / 200  and thus the assembled rail  300  and fence section  500  is variable and will typically be chosen for aesthetic and ease of assembly considerations. Additionally the design of the individual rail components  100 / 200  of the fence rail  300 , allow for the easy construction of the section  500  via laying one of the individual rail components  100 / 200  for each rail  300  to be incorporated onto the ground, then lying the pickets  400  into the picket cutouts  101 . The opposing component  100 / 200  of the fence rail  300  is then snapped into place, locking in the placed pickets  400 . The completed fence section  500  can then be easily lifted into place and secured to the fence posts  600 .  
         [0016]     The fence sections  500  can be easily assembled into a fence system by attachment of the individual sections  500  to fence posts  600  located at regular intervals in the fence system. This attachment can be, but is not limited to, attachment via screws through the post  600  and into the rail component  100 / 200  at the screw boss  150 / 250 . The design structure of the individual fence sections  500  also allow for the individual sections to easily be racked at an angle of up to fifty degrees. That is to allow the use of the fence system on an up or down grade of up to fifty degrees with no substantial loosening of the fence parts or undue torque on the fence components.

Summary:
A picket fence system using two part parallel rails to enclose and secure intermittent pickets, which can be assembled without screws or fasteners is described.