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 OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates generally to retaining devices. More specifically, the present invention relates to a snow guard for installation on a sloped roof to prevent the sudden and unexpected sliding of snow from the roof.  
         [0003]     2. Description of the Related Art  
         [0004]     The accumulation of snow upon roofs can be a major problem in many areas of the world. Generally, roofs tend to be constructed with steeper pitches in areas with greater snowfall in order to allow the snow to slide from the roof slope to avoid excessive snow loads on the roof structure. Steeper roof pitches are also capable of supporting greater snow loads, as well.  
         [0005]     Snow does not typically slide from a sloped structure immediately upon contacting the structure. Rather, the first snow tends to adhere to the underlying structure, with additional snow adhering to the first snow. The buildup continues until a significant amount of snow has accumulated on the structure. When the proper conditions occur, e.g., sufficient mass of snow in combination with sufficient heat radiating through the roof structure to melt the snow immediately adjacent to the roof, the snow tends to release from the sloped structure all at once. This can result in extremely hazardous conditions for anyone immediately beneath the eaves of the roof when the snow slide occurs if sufficient snow has built up, particularly if some melting and refreezing, or freezing rain, has occurred to form large masses of ice.  
         [0006]     Accordingly, various means of controlling the sliding, or avalanching of snow from sloped or gabled roofs have been developed in the past. Various mounting or attachment systems have been used in the past for the installation of snow guards for roofs. An example of such is found in European Patent No. 389,438, published on Sep. 26, 1989, which discloses a series of embodiments of snow guards, with each using a clip principle to hook or catch beneath the edge of a tile on a tiled roof. A retainer is adjustably attached to the hook or catch portion, to clasp the edge of the tile between the two components. The entire snow guard structure must be removed from its attachment to the tiles in order to remove the fence or retainer portion for snow removal from the roof.  
         [0007]     Another example of a snow guard is found in Japanese Patent No. 5-52,063, published on Mar. 2, 1993. According to the drawings and English abstract, the device comprises various embodiments of a snow guard or fence attached along the eaves of the roof. The device comprises a series of horizontal or vertical bars, or an open mesh.  
         [0008]     Yet another example is found in German Patent No. 4,235,478, published on Apr. 28, 1994. The device comprises an elongate mounting bracket having an I-beam cross section, with the upper flange shorter than the lower flange and the web tapering between the two. A single round bar is installed through a passage in the web of the mounting bracket.  
         [0009]     None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a snow guard for roofs solving the aforementioned problems is desired.  
       SUMMARY OF THE INVENTION  
       [0010]     The snow guard for roofs serves to prevent the accidental or unplanned sliding or avalanching of snow from a gabled roof. The device has a series of slotted brackets, which are permanently attached to the roof, preferably through the eaves thereof outside of the walls of the structure. A single, flat snow fence is removably placed in the slots of the mounting brackets. The slots of the brackets preferably extend only partially from the top of the brackets toward their bases, thus elevating the lower edge of the snow fence component above the surface of the roof. This enables the snow guard to be installed upon metal or other roof surfaces having strengthening ribs or ridges extending from the ridgeline to the eaves, with the lower edge of the snow fence clearing the ribs or ridges to avoid damage thereto.  
         [0011]     The mounting brackets may be secured through the metal (or other) roof covering and underlying sheathing, or may be secured through stringers supporting the overlying metal roof sheathing. The slotted mounting brackets permit the snow fence to be quickly and easily lifted from the brackets whenever desired, thus permitting the user of the device to remove accumulated snow from the roof structure in a deliberate manner when safe, rather than risking random snow slides from an unguarded roof.  
         [0012]     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is an environmental, perspective view of a snow guard for roofs according to the present invention, showing its installation and general configuration.  
         [0014]      FIG. 2  is an exploded environmental perspective view of the snow guard of  FIG. 1 , showing an exemplary installation of one of the brackets and the snow fence portion of the device lifted from its receiving slots in the brackets.  
         [0015]      FIG. 3  is an environmental end elevation view of an exemplary sheathed roof structure, showing further installation details of the snow guard of the present invention and alternative slot configurations for the brackets.  
         [0016]      FIG. 4  is an environmental end elevation view of a roof structure having a series of horizontal stringers supporting the sheet roof covering, with the brackets attached through one of the stringers. 
     
    
       [0017]     Similar reference characters denote corresponding features consistently throughout the attached drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     The present invention comprises various embodiments of a snow guard for roofs, serving to prevent random or accidental slippage of snow from a sloped roof, yet allowing a user of the snow guard to deliberately remove snow from the roof as needed. While the snow guard is particularly adapted for use on roofs having sheet metal sheathing or corrugated roofing, it may be used with other types of roofs as well, if so desired.  
         [0019]      FIG. 1  of the drawings provides an environmental perspective view of the snow guard  10  in an exemplary installation on a sloped or gabled roof R covered with sheet metal sheathing M. Such metal sheathing M is generally provided with additional stiffening corrugations C and overlapping seams or joints J, which are raised above the surface of the sheet metal M. The snow guard  10  includes a series of spaced apart snow fence mounting brackets  12 , which are attached to the structure of the roof R, preferably through the eaves E to the exterior of the outer walls of the structure. This eaves installation positions all bracket attachment holes to the outside of the exterior walls, thus precluding any leakage through such holes into the interior of the structure. However, the present snow guard  10  could be secured to the roof R somewhat further toward the roof crest and over the interior of the structure, if so desired.  
         [0020]     Each of the snow fence mounting brackets  12  includes a roof surface attachment flange  14  which rests upon the roof surface M (or other sheathing material) when the brackets  12  are installed atop the roof R. The roof attachment flange  14  of each bracket  12  includes at least one, and preferably two, attachment holes  16  therethrough (visible in the unattached bracket in  FIG. 2 ) for the installation of a corresponding number of roof sheathing through-bolts  18  for securing the brackets  12  to the underlying roof structure R. Preferably through-bolts  18  and nuts  20  ( FIGS. 2 through 4 ) are used to secure the brackets  12  to the roof R, rather than lag screws or similar fasteners that do not penetrate completely through the underlying material.  
         [0021]     The use of through-bolts and nuts provides a much more secure installation for the brackets  12 . By installing the brackets  12  through the eaves E of the roof structure, the mounting holes through the roof sheathing are disposed externally to the walls of the structure so that any leakage through the mounting holes remains to the exterior of the structure, rather than entering the attic or ceiling of the structure. However, the brackets  12  could be installed through the roof structure above the interior of the structure, if so desired. In any event, appropriate sealing or caulking materials (e.g., conventional silicone sealants, etc.) are preferably used to seal the holes through the roof structure in order to preclude water damage to the conventional wood structure and/or leakage therethrough.  
         [0022]     Each of the snow fence mounting brackets  12  includes a snow fence mounting flange  22  extending upwardly therefrom, with the snow fence mounting flange being substantially normal to the roof attachment flange  14  of the corresponding bracket  12 , the brackets  12  being angle brackets or L-shaped brackets. The two flanges  14  and  22  may form a right angle cross section, as shown in  FIGS. 1 and 2 , or may alternatively be in the form of a T section with the snow fence mounting flange  22  joined medially to the roof attachment flange  14 , with both configurations providing the appearance shown in the side elevation views of the brackets  14  shown in  FIGS. 3 and 4 .  
         [0023]     Each snow fence mounting flange  22  has an upper edge  24 , with a snow fence mounting slot  26  extending from the upper edge  24  of the flange  22  toward the roof attachment flange  14 . The slots  26  do not extend completely to the bases of the flanges  22  where they meet their respective roof attachment flanges  14 , but have a lower limit  28  elevated somewhat above the roof attachment flanges  14 . This positions the lower point  28  of each slot  26  somewhat above the surface of the roof R, and particularly above the crests of the stiffening corrugations C and joints J of a corrugated sheet metal M roof surface, as shown in  FIGS. 3 and 4 . In this manner, the lower edge  30  of the snow fence element  32  installed in the slots  26  is positioned or spaced somewhat above the roof surface attachment flange  14  of each of the snow fence mounting brackets  12 , and thus above the underlying corrugations C or joints J of the roof surface, generally as shown in  FIGS. 3 and 4 . This precludes any abrasion or other possible damage to the roof sheathing due to contact with the snow fence  32 , as the snow fence cannot come into direct contact with the roof structure due to its support above the roof by the limited depth of the slots  26  of the mounting brackets  12 .  
         [0024]     The removable snow fence element  32  preferably comprises a single elongate, flat, solid length of material having a thin, rectangular cross section, generally as shown in its end view in  FIGS. 3 and 4 . The snow fence element  32  is preferably formed of a relatively narrow sheet of aluminum plate having sufficient thickness to limit bending due to snow loads thereon, e.g., ±4 inch. Other thicknesses may be used as desired, depending upon the height of the fence element  32 , the anticipated snow loads, the slope of the roof, and the material used for the fence  32 . The slots  26  formed in the snow fence mounting flanges  22  of the mounting brackets have a width corresponding to the thickness of the snow fence element  32 , or very slightly wider in order to avoid interference when installing the fence  32  in the slots  26 . The snow fence  32  rests within the slots  26  of the mounting brackets  12 , and may be removed merely by lifting the fence  32  from the slots  26  for snow removal from the roof as needed. The mounting brackets  12  are also preferably formed of aluminum, with the aluminum material providing superior corrosion resistance in comparison to untreated mild steel. The aluminum may be anodized or coated for further corrosion protection, if so desired. Any suitable materials other than aluminum may be used alternatively to form the brackets  12  and/or snow fence  32 .  
         [0025]      FIG. 3  illustrates alternative slot orientations for the snow fence support or mounting bracket  12 . Preferably, the snow fence mounting slot  32  is normal to the plane of the roof surface attachment flange  14  of each bracket  12 , i.e., forming a right angle to the roof surface attachment flange  14 , and thus to the roof surface as well when the brackets  12  are secured thereto. However, the mounting slots  32  may be cut or otherwise formed at other than a right angle to the attachment flange  14 .  FIG. 3  illustrates this, with alternative slot orientations  26   a  and  26   b  shown in broken lines and forming acute angles to the plane of the attachment flange  14  and underlying roof surface. In the case of the alternative slot position  26   a , the slot  26   a  is sloped toward the crest of the roof to form an upslope acute angle with the roof surface. The other alternative slot position  26   b  forms a downslope acute angle toward the eaves edge. The angle of the slot  26   a  or  26   b  may be formed as desired, depending upon the anticipated snow loads, the slope of the roof, and perhaps other factors as well.  
         [0026]      FIG. 4  of the drawings illustrates the installation of the present snow guard  10  upon the eaves E of a roof R having a somewhat different structure than that shown in  FIG. 3 . The roof structure R of  FIG. 4  utilizes a series of horizontal stringers S installed across the slopes of the roof rafters or beams B, with the metal roof sheathing M attached directly to the stringers rather than to continuous underlying sheathing. Accordingly, the snow fence mounting brackets  12  are attached through the stringers S by means of through-bolts  18  and nuts  20  in order to provide sufficient attachment strength. The attachment of the brackets  12  through the relatively thin sheet metal M would not provide sufficient strength for the assembly, and would likely result in damage to the sheet metal M with any appreciable snow load.  
         [0027]     In conclusion, the snow guard for roofs provides protection from snow slides or avalanches from a snow accumulation upon a sloped or gabled roof structure. Rather than being permanently attached to the roof structure, the snow fence itself is removably placed within the slots of the mounting brackets to hold any snow accumulation atop the roof until removal is desired. When it is desired to remove the snow accumulation from the roof, the user need only lift the snow fence from its position in the mounting bracket slots, and possibly rake or otherwise move any accumulated snow from the roof past the eaves of the roof to fall upon the surface below. The snow guard permits the user to select the time for snow removal, rather than the snow randomly slipping from the roof and perhaps injuring persons or property below. The snow guard is particularly well adapted for installation upon roofs having sheet metal sheathing or covering, but may be adapted to other roof types as well. Accordingly, the present snow guard for roofs will prove to be a popular and valuable addition to roof structures in areas where snow accumulation is a problem or occurrence.  
         [0028]     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.

Summary:
The snow guard for roofs includes a plurality of slotted brackets, which are permanently installed atop the roof structure. A snow fence is removably installed in the slots of the brackets, permitting the user to remove the fence as needed for the deliberate removal of snow from the roof in a safe and predetermined manner. The slots of the brackets extend only partially toward the bottoms of the brackets, thus placing the lower edge of the snow fence elevated above the underlying roof structure. This provides clearance between the snow fence and any strengthening ribs or ridges formed in the roof covering, as are typically provided in sheet metal covered roofs. The brackets are preferably attached along the eaves of the roof outboard of the wall structure to preclude leakage through the mounting holes and water damage to the interior of the structure.