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: 
SUMMARY OF THE INVENTION 
     This invention relates to roof edging mechanisms used to secure the edges of a roof-top waterproof membrane and more particularly to an uncomplicated roof edge fascia system designed to act as a gravel curb, a moisture seal and an aesthetically appealing finishing trim around such roof-top edges. 
     The use of roof edge fascia systems to secure the edges of roof-top waterproof membranes is well known. However, in his many years of experience in the art with which the invention is concerned, the inventor has obtained no knowledge of any roof edge fascia system which possesses the uncomplicated essential features of the present invention. Furthermore, roof edge fascia systems disclosed in the prior art, such as that disclosed in U.S. Pat. No. 4,037,372 which shows a cover plate 32 interlockingly engaging a fascia receiver 30 (see FIGS. 1-4), are generally more complicated in design than the system of the present invention and are correspondingly more expensive to fabricate and more difficult to assemble in the field. 
     It is therefore, a principal object of this invention to provide a new, useful and uncomplicated roof edge fascia system which is economically fabricated, easily assembled in the field and which accomplishes all of this while creating an aesthetically appealing fascia system from all points outside of the building. 
     The present invention has obtained these objects by providing for a base member adapted to overlay and anchor the edge of a roof-top waterproof membrane to the roof edge and by providing a complemental face plate member adapted to interlockingly engage the base member. The base member comprises a metal extrusion and includes an upwardly extending portion, said portion having a channel, and a downwardly extending portion. The face plate member comprises a sheet metal material so formed as to include first and second bent-over end portions in symmetrical opposition to each other. The bent-over end portions are interchangeably adapted such that the first (or second) bent-over end portion fits over the downwardly extending portion of the loose member and the second (or first) bent-over end portion fits over and snaps into the channel of the upwardly extending portion of the base member. In this configuration, installation of the face plate member in the field is facilitated since either bent-over end portion may be used to fit over either portion of the base member. After installation, the complemental face plate member is rigidly held in place, thereby preventing the entry of water between the base member and the face plate member. The foregoing and other features of the present invention will be further apparent from the description that follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a vertical sectional view through the roof edging mechanism as installed on a roof edge. 
    
    
     DETAILED DESCRIPTION 
     Reference is now made more particularly to the drawing which shows the roof edge system constructed in accordance with the present invention. As shown, a waterproof membane 5 overlays and is secured to a wood nailer 2 located at the top of a wall 1. Means for securing the membrane 5 to the roof edge is provided by base member generally identified 10 which is comprised of an extruded metal material and includes a vertical hold down portion 11 and a foot portion 12. The hold down portion 11 of the base member 10 includes a hole 13 through which a fastener 6 secures the base member 10 to the wood nailer 2, thereby compressibly clamping the ede of the membrane 5 between the vertical portion 11 and foot portion 12 of the base 10 and the nailer 2. The base member 10 further includes an upwardly extending portion 14 and a downwardly extending portion 18. The upwardly extending portion 14 includes a lower flange 15 and an upper flange 16, said upper flange 16 having a projecting ridge member, which define a channel 17 at the uppermost portion of the upwardly extending portion 14. 
     Means for covering the base member 10 is provided by face plate member generally identified 20 which is comprised of a sheet metal material having a vertical portion 21 and first and second bent-over end portions 22, 22a and first and second reverse bend end portions 23, 23a. The bent-over end portions 22, 22a, and reverse bend end portions 23, 232 further define first and second end portion openings 24, 24a at each end of the face plate member 20. The openings 24, 24a are adapted to engage either of the upwardly or downwardly extending base member portions 14, 18. Furthermore, both reverse bend end portions 23, 23a are adapted to interlockingly engage the channel 17 of the upwardly extending portion 14. 
     During installation of the roof edge system of the present invention, the base member 10 overlays the membrane 5 and is fastened to the wood nailer 2 by means of the fastener 6 extending through the hole 13 of the vertical hold down portion 11 of said base member 10. With the base member 10 in place, the waterproof membrane 5 is compressed so as to provide a water-tight seal at the edge of the roof. While not shown, the waterproof membrane 5 may be further imbedded in a sealant type material. A sealant bead 25 may also be applied. After the base member 10 is in place, the first end portion opening 24 defined by the first bent-over end portion 22 of the face plate 20 is engaged with and pushed upwardly along the downwardly extending portion 18 of the base member 10. The second or opposite end portion opening 24a defined by the second bent-over end portion 22a is then aligned generally vertically in relation to the upwardly extending portion 14 of the base member 10. The second end portion opening 24a is then urged downwardly toward the upper flange 16 of the upwardly extending portion 14 until the reverse bend end portion 23a overlaps the projecting ridge member of said upper flange 16 and engages the channel 17. This interlock concept greatly facilitates installation of the face plate member 20 because either bent-over end portion 22, 22a can be used to initiate installation. After installation, the face plate member 20 is held rigidly in place thereby preventing the entry of water between the face plate 20 and the base member 10. 
     From the foregoing detailed description of the illustrative embodiment of the invention set forth herein, it will be apparent that there has been provided a new, useful and uncomplicated roof edge fascia system which is economically fabricated, easily assembled in the field and which accomplishes all of this while creating an aesthetically appealing fascia system from all points outside of the building to which it is applied.

Summary:
A roof edge fascia system has a base member to secure the edges of a roof-top waterproof membrane at a roof edge and an invertible complemental fascia member transposably interlockable with the base member.