referring now to fig1 , there is shown a front elevational view of a storm door consistent with the present invention . the storm door of fig1 is an example of a self - storing storm door . it should be understood , however , that the storm door can be designed differently , such as a full view storm door or a crossbuck door , and that the following description with respect to a self - storing storm door is for exemplary purposes only . as shown in fig1 , the storm door includes a pair of horizontal sashes or rails 1 , 2 and a pair of vertical sashes or rails 3 , 4 . the horizontal rail 1 is coupled at respective ends to a top end of the vertical sashes 3 , 4 , and the horizontal rail 2 is coupled at respective ends to a bottom end of the vertical sashes 3 , 4 . the combination of the horizontal rails 1 , 2 and the vertical sashes 3 , 4 forms a frame of the storm door of fig1 . the horizontal rails 1 , 2 and the vertical sashes 3 , 4 are preferably formed with pvc , although other materials may be used . the storm door of fig1 also includes a pair of sash muntins 5 , 6 that divide the storm door into three sections . the sash muntins 5 , 6 can be formed of pvc , aluminum , or some other lightweight material . a top section 7 preferably holds a window or glass pane . the window in top section 7 can be set in a fixed position . the middle section 8 preferably holds a window or glass pane and / or a screen . the window pane and screen may be slidable between the middle section 8 and the top section 7 so that either both or one is present in the middle section 8 at one time . it is also possible for the window pane and the screen to be respectively replaceable , i . e ., one is popped or screwed into place at a time in the middle section 8 . a bottom section 9 preferably holds a fixed pvc panel , although the panel can be formed from other materials . the storm door of fig1 further includes a handle 10 for locking , opening , and closing the storm door . a plurality of hinges 11 are used to mount the storm door in a door frame of a home or building . although the handle 10 is shown on the right side and the hinges 11 are shown on the left side of the storm door , it should be understood that the handle 10 and the hinges 11 can be reversed . in either position , the handle 10 and the hinges 11 are preferably positioned on the opposite sides of the storm door . fig2 is a sectional view taken along the lines a - a of fig1 . the sectional view of fig2 shows details of the internal construction of the horizontal rails 1 , 2 . in particular , the horizontal rails 1 , 2 each include an internal steel reinforcement portion 12 . the internal steel reinforcement portion 12 is a relatively thin layer of steel and preferably has a substantially u - shaped or rectangular - shaped cross section . in addition , the internal steel reinforcement portion 12 preferably has a hollow core . the internal steel reinforcement portion 12 is formed to be in contact with or very nearly in contact with the exterior pvc portion of the horizontal rails 1 , 2 . in addition to the internal steel reinforcement portion 12 , each of the horizontal rails 1 , 2 includes a part of a corner reinforcement portion 13 . there is a part of the corner reinforcement portion 13 in each end of the horizontal rails 1 , 2 . the corner reinforcement portions 13 are preferably formed from pvc or other sturdy plastic material . the corner reinforcement portions 13 are preferably formed to have a substantially rectangular or square - shaped cross - section with a hollow core . the thickness of the corner reinforcement portions 13 is preferably greater than the thickness of the steel reinforcement portions 12 . the exterior pvc portion of the horizontal rails 1 , 2 is coupled to the steel reinforcement portions 12 and the corner reinforcement portions 13 by screws 14 . although the coupling is shown as screws 14 , it should be understood that other coupling elements as are known in the art can be used to connect the exterior pvc portion of the horizontal rails 1 , 2 to the steel reinforcement portions 12 and the corner reinforcement portions 13 . fig2 also shows an internal support section 15 , which is preferably made of pvc or aluminum . fig3 is a sectional view taken along the lines b - b of fig1 . fig4 is a sectional view taken along the lines c - c of fig1 . the sectional views of fig3 and 4 show details of the internal design of the vertical rails 3 , 4 . in particular , like the horizontal rails 1 , 2 , the vertical rails 3 , 4 each include an internal steel reinforcement portion 12 preferably having the same thickness and design as that of the horizontal rails 1 , 2 . the vertical rails 3 , 4 also include a part of a corner reinforcement portion 13 positioned in each end of the vertical rails 3 , 4 . the exterior pvc portion of the vertical rails 3 , 4 is also coupled to the steel reinforcement portions 12 and the corner reinforcement portions 13 by screws 14 . fig3 also shows an internal support section 15 , which is preferably made of pvc or aluminum . in general , the internal steel reinforcement portions 12 provide stability to the storm doors . more specifically , the internal steel reinforcement portions and serve as a core fig5 shows a detailed cutaway view of a corner portion of the storm door including a complete corner reinforcement portion 13 . the corner shown in fig5 is for the corner joining the horizontal rail 2 and the vertical rail 4 . it should be understood , however , that the view shown in fig5 is applicable to each of the other corners of the storm door . as shown in fig5 , a part of the corner reinforcement portion 13 is present in the horizontal rail 2 , and a part of the corner reinforcement portion 13 is present in the vertical rail 4 . as also shown in fig5 , the ends of the exterior pvc portions of the horizontal rail 2 and the vertical rail 4 are mitered at 45 degree angles such that , when the respective ends are joined together , the horizontal rail 2 and the vertical rail 4 form a 90 degree angle . the ends of the corner reinforcement portions 13 in the horizontal rail 2 and the vertical rail 4 are likewise formed in such a manner . as shown in fig5 , the corner reinforcement portions 13 extend only part way into the horizontal rail 2 and the vertical rail 4 . in an alternative embodiment , it is possible for the corner reinforcement portions 13 to extend the entire length or a greater portion of the horizontal rail 2 and the vertical rail 4 . fig5 also shows that the internal steel reinforcement portions 12 extend substantially to the end of the horizontal rail 2 and the vertical rail 4 , but not as far as the corner reinforcement portions 13 . the internal steel reinforcement portions 12 preferably extend as close as possible to the end of the horizontal rail 2 and the vertical rail 4 to provide additional support for them . two pairs of screws 14 are positioned adjacent to the corner of the storm door . the two pairs of screws 14 near each corner of the storm door can be the only elements coupling the exterior pvc portion of the horizontal rails 1 , 2 and vertical rails 3 , 4 to the respective steel reinforcement portions 12 and corner reinforcement portions 13 . alternatively , additional screws 14 can be used for the coupling in each rail . the horizontal rail 2 and the vertical rail 4 are preferably coupled together at the respective exterior pvc portions and at the respective corner reinforcement portions 13 . the coupling can be made , for example , with a pvc weld . alternatively , the rails can be coupled together with a metal bracket or other couplings as are known in the art . the foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description . it is not intended to be exhaustive or to limit the invention to the precise form disclosed , and modifications and variations are possible in light in the above teachings or may be acquired from practice of the invention . the embodiments ( which can be practiced separately or in combination ) were chosen and described in order to explain the principles of the invention and as practical application to enable one skilled in the art to make and use the invention in various embodiments and with various modifications suited to the particular use contemplated . it is intended that the scope of the invention be defined by the claims appended hereto and their equivalents .