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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates, in general, to temporary support structures used in soft and environmentally sensitive areas to construct roads and pads to support heavy equipment and the like. 
     2. Information Disclosure Statement 
     Wooden mats and roads have been utilized for many years particularly in the oil and gas industry to provide temporary roads and pads for construction equipment and heavy trucks in areas that are environmentally sensitive or inaccessible due to poor soil conditions during the rainy part of the year. These roads and mats are typically constructed one piece at a time and are very time consuming and labor intensive to construct. 
     As pressure on labor markets increased and time constraints on construction tightened, some mat systems appeared on the market, and worked well to relieve the labor and time problems. However, when the wooden mats are laid piece by piece, the number of plys of lumber were determined by the soil conditions and the size of the loads to be hauled across them. The mat systems commonly used today are three ply systems. As a general rule, fewer plies of lumber are required to accomplish the same result as elevation increases above sea level. For example, a mat having four plys of lumber may be necessary to support typical oil industry equipment over a wet site close to sea level, while a mat having only two plys of lumber may be adequate to support the same equipment over a dryer site located well above sea level, etc. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for temporary matting for use on constructions sites to satisfy the aforementioned needs. 
     The mat of the present invention includes, in general, a bottom ply having a first end edge, a second end edge, a first side edge, a second side edge, and at least a first opening therethrough; and a top ply having a first end edge, a second end edge, a first side edge, a second side edge, at least a first slot extending into the first end edge of the top ply, at least a first tab aligned with the first slot in the first end edge of the top ply to and extending out of the second end edge of the top ply, and at least a first opening therethrough; the top and bottom plies are attached to one another with the first opening of the top ply positioned over the first opening of said bottom ply, with said first end edges of the top and bottom plies substantially aligned with one another so that the first slot of the top ply extends over a portion of the bottom ply, and with the second end edges of said top and bottom plies substantially aligned with one another so that the first tab of said top ply extends outward of the bottom ply. 
     It is an object of the present invention to provide a temporary support structure comprising a two ply, interlocking mat system that minimizes costs and maximizes the use of labor, equipment and material to provide temporary access to construction sites regardless of weather and soil conditions. 
     It is another object of the present invention to provide such a temporary support structure comprised of a plurality of two ply mats of rectangular configuration that interlock with slots or tabs on all sides of the mat. 
     It is another object of the present invention to provide such a temporary support structure in which the upper and lower layer of each mat are perpendicular and all boards on each layer are uniformly spaced to minimize cracks and maximize strength of the mat. 
     It is another object of the present invention to provide such a temporary support structure in which the slots and tabs on each mat are uniformly spaced and of sufficient length so that, when two or more mats are properly butted or joined together, every slot and tab is overlapped by at least it&#39;s width. 
     It is another object of the present invention to provide such a temporary support structure which provides a very stable working area when the mats are locked together using the slots and tabs on the side of the mats, because the slots and tabs of the surrounding mats hold each mat in place. 
     It is another object of the present invention to provide such a temporary support structure in which a temporary road or pad can be constructed by lifting the mats with forklifts, cranes or other suitable equipment 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective view of a first embodiment of the mat of the present invention. 
     FIG. 2 is a top plan view of the mat of FIG.  1 . 
     FIG. 3 is a top plan view of the bottom ply or layer of the mat of FIG.  1 . 
     FIG. 4 is a top plan view of the top play or layer of the mat of FIG.  1 . 
     FIG. 5 is a diagrammatic top plan view of several of the mats of FIG. 1 joined and being joined to one another to construct a road, including mats of different lengths. 
     FIG. 6 is a sectional view substantially as taken on line  6 — 6  of FIG. 5, on a somewhat enlarged scale. 
     FIG. 7 is a perspective view of a second embodiment of the mat of the present invention. 
     FIG. 8 is a top plan view of the mat of FIG.  7 . 
     FIG. 9 is a top plan view of the bottom ply or layer of the mat of FIG.  7 . 
     FIG. 10 is a top plan view of the top ply or layer of the mat of FIG.  7 . 
     FIG. 11 is a diagrammatic top plan view of several of the mats of FIG. 7 joined and being joined to one another to construct a pad. 
     FIG. 12 is a sectional view substantially as taken on line  12 — 12  of FIG. 11, rotated 90° and on a somewhat enlarged scale. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     A first embodiment of the mat of the present invention is shown in FIGS. 1-6 and identified by the numeral  11 . The mat  11  is designed for use in combination with a plurality of similar mats to provide a temporary support structure used to construct roads and pads to support heavy equipment. The mat  11  is especially designed for the construction of temporary roads to support heavy construction equipment and trucks typically used in the oil and gas industry and in logging, etc. 
     The mat  11  includes a bottom ply or layer  13  and a top ply or layer  15 . 
     The bottom ply  13  may be constructed from a plurality of boards  17  of the same basic size. Thus, for a standard road, the bottom ply  13  is constructed from a plurality of 2 inches (5.08 centimeters) thick by 8 inches (20.32 centimeters) wide by 11.5 feet (3.5 meters) long lumber. Alternatively, the lumber could be 10 feet (3.05 meters) long. Each board  17  is arranged parallel and preferably spaced from one another an equal distance, e.g., 4 inches (10.16 centimeters). The number of boards  17  used to construct the bottom ply  13  can vary, depending on the length of mat  11  desired. Thus, for example, for a mat  11  that is 12 feet (3.7 meters) long, the bottom ply  13  preferably includes 12 boards  17 . Similarly, for a mat  11  that is 14 feet (4.3 meters) long, the bottom ply  13  preferably includes 14 boards  17 ; and for mat  11  that is 16 feet (4.9 meters) long, the bottom play  13  preferably includes 16 boards  17 . 
     While each of the boards  17  are preferably coextensive with one another, the middle portion of one or more of the boards  17  are preferably cut away to form a gap or opening  19  between the opposite ends of that board or boards  17 . Thus, with respect to the 12 foot mat  13  shown in the drawings, the middle portion of the third and fifth boards  17  from each end is cut away to form the gaps or openings  19 . 
     The top ply  15  may include a first track or runner  21  and a second track or runner  23 . The runners  21 ,  23  support the wheels, etc., of heavy construction equipment and trucks typically used in the oil and gas industry and in logging, etc. In the preferred embodiment, each runner  21 ,  23  of the top ply  15  is constructed from a plurality of boards  25  of the same basic size. Thus, for a standard road, each runner  21 ,  23  is constructed from a plurality of 2 inches (5.08 centimeters) thick by 8 inches (20.32 centimeters) wide lumber. The length of each board  25  depends on the desired sized of the mat  11 . Thus, for a mat  11  that is 12 feet (3.7 meters) long, each board  25  is preferably 12 feet (3.7 meters) long. Similarly, for a mat  11  that is 14 feet (4.3 meters) long, each board  25  is preferably 14 feet (4.3 meters) long; and for mat  11  that is 16 feet (4.9 meters) long, each board  25  is preferably 16 feet (4.9 meters) long. Each board  25  is arranged parallel and preferably spaced from one another an equal distance, e.g., 1 inches (2.54 centimeters). While the number of boards  25  used to construct each runner  21 ,  23  can vary, for a typical road each runner  21 ,  23  preferably includes five boards  25 . 
     While each of the boards  25  are preferably the same length, the middle board or boards  25  of each runner  21 ,  23  are offset with respect to the outside boards  25  of each runner  21 ,  23  so that a slot  27  is formed at one end of each runner  21 ,  23  and a tab  29  is formed at the other end of each runner  21 ,  23 . With respect to the mat  11  shown in the drawings, the middle three boards  25  of each five board runner  21 ,  23  is so offset. 
     The boards  25  of the top ply  15  are securely attached to the boards  17  of the bottom ply  13 , using bolts, nails, glue, etc., with the longitudinal axis of each board  25  substantially perpendicular to the longitudinal axis of each board  17 , and with the runners  21 ,  23  substantially parallel to one another and centered between the opposite ends of each board  17  with a space therebetween to locate the centerline of each runner  21 ,  23  the appropriate distance to support the wheels of heavy construction equipment and trucks typically used in the oil and gas industry and in logging, etc. Thus, the runners  21 ,  23  are preferably spaced apart approximately 26 inches (66.04 centimeters). 
     In addition to the runners  21 ,  23 , the top ply  15  preferably includes a plurality of reinforcing boards  31  attached to a plurality of the boards  17  of the bottom ply  13  in the space between the runners  21 ,  23 . Thus, the top ply  15  may include three reinforcing boards  31  attached to the first two, last two and middle two boards  17  of the bottom ply  13  for strengthening the first two, last two and middle two boards  17  of the bottom ply  13 . The reinforcing boards  31  are preferably constructed from 2 inches (5.08 centimeters) thick by 8 inches (20.32 centimeters) wide by 20 inches (50.8 centimeters) long lumber, spaced apart from one another approximately 0.5 inches (1.27 centimeters). A set of reinforcing boards  31  are thus located adjacent each gap  19 , and coact with the gaps  19  and the portion of the boards  17  covered by the reinforcing boards  31  to form means for allowing the mat  11  to be easily grabbed with grapple of a knuckleboom, a crane, a forklift truck, etc., for pick up, moving, laying, etc. The reinforcing boards  31  strengthen the associated boards  17  to prevent damage to the mat  11  when those boards  17  are clamped by a grapple, etc. 
     Second Embodiment 
     A second embodiment of the mat of the present invention is shown in FIGS. 7-12 and identified by the numeral  2 . 11 . The mat  2 . 11  is also designed for use in combination with a plurality of similar mats to provide a temporary support structure used to construct roads and pads to support heavy equipment, but is especially designed for the construction of temporary pads to support heavy construction equipment and trucks typically used in the oil and gas industry and in logging, etc. 
     The mat  2 . 11  includes a bottom ply or layer  2 . 13  and a top ply or layer  2 . 15 . 
     The bottom ply  2 . 13  may be constructed from a plurality of boards  2 . 17  of the same basic size. Thus, for a standard pad, the bottom ply  2 . 13  may be constructed from a plurality of 2 inches (5.08 centimeters) thick by 8.25 inches (20.95 centimeters) wide by 8 feet (2.4 meters) long lumber. Each board  2 . 17  is arranged parallel and preferably spaced from one another an equal distance, e.g., 2.125 inches (5.3975 centimeters). The number of boards  2 . 17  used to construct the bottom ply  2 . 13  can vary, depending on the length of mat  2 . 11  desired. Thus, for example, for a mat  2 . 11  that is 12 feet (3.7 meters) long, the bottom ply  2 . 13  preferably includes 14 boards  2 . 17 . Similarly, for a mat  2 . 11  that is 10 feet (3.05 meters) long, the bottom play  2 . 13  preferably includes  12  boards  2 . 17 ; for a mat  2 . 11  that is 14 feet (4.3 meters) long, the bottom ply  2 . 13  preferably includes 16 boards  2 . 17 ; and for mat  2 . 11  that is 16 feet (4.9 meters) long, the bottom play  2 . 13  preferably includes 18 boards  2 . 17 . 
     While each of the boards  2 . 17  are preferably the same length, each adjacent board  2 . 17  is preferably offset or staggered with respect to one another so that, in combination with the top ply  2 . 15 , a slot  2 . 19  is formed at one end of each board  2 . 17  and a tab  2 . 21  is formed at the other end of each board  2 . 17 . 
     The top ply  2 . 15  may be constructed from a plurality of boards  2 . 23  of the same basic size. Thus, for a standard pad, the bottom ply  2 . 15  may be constructed from a plurality of 2 inches (5.08 centimeters) thick by 8.25 inches (20.95 centimeters) wide lumber. The length of each board  2 . 23  depends on the desired sized of the mat  2 . 11 . Thus, for a mat  2 . 11  that is 12 feet (3.7 meters) long, each board  2 . 23  is preferably 12 feet (3.7 meters) long. Similarly, for a mat  2 . 11  that is 10 feet (3.05 meters) long, each board  2 . 23  is preferably 10 feet (3.05 meters); for a mat  2 . 11  that is 14 feet (4.3 meters) long, each board  2 . 23  is preferably 14 feet (4.3 meters) long; and for mat  2 . 11  that is 16 feet (4.9 meters) long, each board  2 . 23  is preferably 16 feet (4.9 meters) long. 
     Each board  2 . 23  is arranged parallel and preferably spaced from one another an equal distance, e.g., 1 inches (2.54 centimeters). While the number of boards  2 . 23  used to construct the top ply  2 . 15  can vary, for a bottom ply  2 . 13  formed of boards  2 . 17  that are 8 feet (2.4 meters) long, the top ply  2 . 15  preferably includes ten boards  2 . 23 . 
     While each of the boards  2 . 23  are preferably the same length, each adjacent board  2 . 23  is preferably offset or staggered with respect to one another so that, in combination with the bottom ply  2 . 13 , a slot  2 . 25  is formed at one end of each board  2 . 23  and a tab  2 . 27  is formed at the other end of each board  2 . 23 . 
     The boards  2 . 23  of the top ply  2 . 15  are securely attached to the boards  2 . 17  of the bottom ply  2 . 13 , using bolts, nails, glue, etc., with the longitudinal axis of each board  2 . 23  substantially perpendicular to the longitudinal axis of each board  2 . 17 . 
     To form the slots and tabs  2 . 19 ,  2 . 21 ,  2 . 25 ,  2 . 27 , and with reference to the layout of the mat  2 . 11  as shown in the drawings, the bottom and top plies  2 . 13 ,  2 . 15  are attached to one another with the left most or first board  2 . 23  of the top ply  2 . 15  substantially aligned with the left most end of left most extending boards  2 . 17  of the bottom ply  2 . 13 , and the uppermost board  2 . 17  of the bottom ply  2 . 13  substantially aligned with the upper most end of the upper most extending board  2 . 23  of the top ply  2 . 15 , so that each slot  2 . 19  of the bottom ply  2 . 13  will be overlapped by a portion of the left most board  2 . 23  of the top ply  2 . 15  by a distance at least equal to its width, and so that each slot  2 . 25  of the top ply  2 . 15  will be overlapped by a portion of the upper most board  2 . 17  of the bottom ply  2 . 13 . 
     First Preferred Embodiment 
     The preferred embodiment of the bottom ply  13  includes a first board section  32  having a first end  33  and a second end  34 ; a second board section  35  extending parallel to the first board section  32  and having a first end  36  positioned conterminous with the first end  33  of the first board section  32  and a second end  37  positioned intermediate the first and second ends  33 ,  34  of the first board section  32 ; a third board section  38  extending parallel to the first board section  32  and having a first end  39  positioned intermediate the first and second ends  33 ,  34  of the first board section  32  and a second end  40  positioned conterminous with the second end  34  of the first board section  32 ; and a fourth board section  41  extending parallel to the first board section  32  and having a first end  42  positioned conterminous with the first end  33  of the first board section  32  and a second end  43  positioned conterminous with the second end  34  of the first board section  32 . The third board section  43  of the bottom ply  13  is aligned with the second board section  35  thereof, and the second and third board sections  35 ,  38  are positioned intermediate the first and fourth board sections  32 ,  41  of the bottom ply  13 . The bottom ply  13  has a bottom gap or opening  19  formed between the second end  37  of the second board section  35  and the first end  39  of the third board section  38 , and between the first and second board sections  32 ,  41 . 
     The preferred embodiment of the top ply  15  includes a first board section  45  having a first end  46  and a second end  47 , and a second board section  48  having a first end  49  and a second end  51 . The first board section  45  of the top ply  15  is attached to and extends perpendicular to the first, second and fourth board sections  32 ,  35 ,  41  of the bottom ply  13  adjacent the first ends  33 ,  36 ,  42  of the first, second and fourth board sections  32 ,  35 ,  41  of the bottom ply  13 . The second board section  48  of the top ply  15  is attached to and extends perpendicular to the first, third and fourth board sections  32 ,  38 ,  41  of the bottom ply  13  adjacent the second ends  34 ,  40 ,  43  of the first, third and fourth board sections  32 ,  38 ,  41  of the bottom ply  13 . The first and second board sections  45 ,  48  of the top ply  15  are spaced apart from one another with the space between the first and second board sections  45 ,  48  generally overlying a bottom gap  19 . 
     The bottom ply  13  preferably includes a fifth board section  55  extending parallel to the first board section  32  thereof and having a first end  57  positioned conterminous with the first end  33  of the first board section  32  and a second end  59  positioned intermediate the first and second ends  33 ,  34  of the first board section  32 ; a sixth board section  61  extending parallel to the first board section  32  thereof and having a first end positioned intermediate the first and second ends  33 ,  34  of the first board section  32  and a second end  65  positioned conterminous with the second end  34  of the first board section  32 ; and a seventh board section  67  extending parallel to the first board section  32  and having a first end positioned  69  conterminous with the first end  33  of the first board section  32  and a second end  71  positioned conterminous with the second end  34  of the first board section  32  of the bottom ply  13 . The sixth board section  61  of the bottom ply  13  is aligned with the fifth board section  55  thereof, and the fifth and sixth board sections  55 ,  61  are positioned intermediate the fourth and seventh board sections  41 ,  67  of the bottom ply  13 . The bottom ply  13  preferably has another bottom opening or gap  19  formed between the second end  59  of the fifth board section  55  and the first end  63  of the sixth board section  61  thereof, and between the fourth and seventh board sections  41 ,  67  thereof. 
     The bottom ply  13  preferably includes a eighth board section  75  extending parallel to the first board section  32  thereof and having a first end  77  positioned conterminous with the first end  33  of the first board section  32  and a second end  79  positioned intermediate the first and second ends  33 ,  34  of the first board section  32 ; a ninth board section  81 extending parallel to the first board section  32  thereof and having a first end  83  positioned intermediate the first and second ends  33 ,  34  of the first board section  32  and a second end  85  positioned conterminous with the second end of the first board section  32  of the bottom ply  13 ; and a tenth board section  87  extending parallel to the first board section  32  thereof and having a first end  89  positioned conterminous with the first end  33  of the first board section  32  and a second end  91  positioned conterminous with the second end  34  of the first board section  32  of the bottom ply  13 . The eighth and sixth ninth board sections  75 ,  81  of the bottom ply  13  are positioned intermediate the seventh and tenth board sections  67 ,  87  thereof and the ninth board section  81  is aligned with the eighth board section  75  thereof. The bottom ply  13  preferably has another bottom opening or gap  19  formed between the second end  79  of the eighth board section  75  and the first end  83  of the ninth board section  81  thereof, and between the seventh and tenth board sections  67 ,  87  thereof. 
     The bottom ply  13  preferably includes an eleventh board section  95  extending parallel to the first board section  32  thereof and having a first end  97  positioned conterminous with the first end  33  of the first board section  32  and a second end  99  positioned intermediate the first and second ends  33 ,  34  of the first board section  32  thereof; a twelfth board section  101  extending parallel to the first board section  32  of the bottom ply  13  and having a first end  103  positioned intermediate the first and second ends  33 ,  34  of the first board section  32  and a second end  105  positioned conterminous with the second end  34  of the first board section  32  of the bottom ply  13 ; and a thirteenth board section  107  extending parallel to the first board section  32  thereof and having a first end  109  positioned conterminous with the first end  33  of the first board section  13  and a second end  111  positioned conterminous with the second end  34  of the first board section  32  of the bottom ply  13 . The eleventh and twelfth board sections  95 ,  101  of the bottom ply  12  are positioned intermediate the tenth and thirteenth board sections  87 ,  107  thereof, and the twelfth board section  101  is aligned with the eleventh board section  95  of the bottom ply  13 . The bottom ply  13  has another bottom opening or gap  19  formed between the second end  99  of the eleventh board section  95  and the first end  103  of the twelfth board section  101  of the bottom ply  13 . 
     The top ply  15  preferably includes a third board section  115  attached to and extending perpendicular to the first board section  32  of the bottom ply  13  between the first and second board sections  45 ,  48  of the top ply  15 , and having a first end  117  and a second end  119 . The top ply  15  preferably includes a fourth board section  121  attached to and extending perpendicular to the seventh board section  67  of the bottom ply between the first and second board sections  45 ,  48  of the top ply  15 , and having a first end  123  and a second end  125 . The top ply  15  preferably includes a fifth board section  127  attached to and extending perpendicular to the thirteenth board section  107  of the bottom ply  13  between the first and second board sections  45 ,  48  of the top ply  13 , and having a first end  129  and a second end  131 . The space between the first and second board sections  45 ,  48  of the top ply  13  is preferably divided into a first top space or gap  133  between the first and second board sections  45 ,  48  and between the third and fourth board sections  115 ,  121  for being aligned over one or more bottom gaps  19  with the intermediate portion of the fourth board section  41  of the bottom ply  13  extending thereacross; and a second top space or gap  135  between the first and second board sections  45 ,  48  and between the fourth and fifth board sections  121 ,  127  for being aligned over one or more bottom gaps  19  with the intermediate portion of the tenth board section  87  of the bottom ply  13  extending thereacross. 
     The mats  11  may be constructed in various manners and out of various materials, and in various sizes as will now be apparent to those skilled in the art. As hereinabove indicated, each of the board sections of the bottom and top plies  13 ,  15  preferably include a plurality of parallel boards. Each individual board of each board section of the bottom ply  13  are preferably coextensive with each other individual board of that board section (i.e., each individual board of each board section is of equal length and the opposite ends are aligned with each other individual board of that board section). As indicated above, each runner  21 ,  23  (i.e., each first and second board section  45 ,  48 ) of the top ply  15  may be constructed from a plurality of individual parallel boards with the opposite ends of the middle individual parallel boards being offset from the opposite ends of the outer individual parallel boards an amount to form the interlocking slots and tabs  27 ,  29 . The bottom and top plies  13 ,  15  can be built out of standard hardwood lumber using a jig or the like to insure precise placement and squareness, with the individual boards of the bottom and top plies  13 ,  15  fastened together by means of bolts, nails, glue, etc. The word “board” is used herein to define any generally long, rectangular, thin piece of lumber or other substantially rigid material, preferably having a shear stress substantially equal to or greater than that of typical hardwood lumber, etc. The phrase “board section” is used herein to define a board that is composed either from a single, unitary member or a plurality of individual members, or boards, joined together. 
     Second Preferred Embodiment 
     A second embodiment of the mat of the present invention is shown in FIGS. 7-12 and identified by the numeral  2 . 11 . The mat  2 . 11  is also designed for use in combination with a plurality of similar mats to provide a temporary support structure used to construct roads and pads to support heavy equipment. The mat  2 . 11  is especially designed for the construction of temporary pad to support heavy construction equipment typically used in the oil and gas industry and in logging, etc. 
     The mat  2 . 11  includes a bottom ply or layer  2 . 13  and a top ply or layer  2 . 15 . 
     The bottom ply  2 . 13  includes a first bottom ply board  2 . 28  having a first end  2 . 29  and a second end  2 . 30 , a second bottom ply board  2 . 31  having a first end  2 . 32  and a second end  2 . 33  positioned adjacent the first bottom ply board  2 . 28 , a third bottom ply board  2 . 34  positioned adjacent the second bottom ply boards  2 . 31  and having a first end  2 . 35  and a second end  2 . 36 , and a fourth bottom ply board  2 . 37  positioned adjacent the third bottom ply boards  2 . 34  and having a first end  2 . 38  and a second end  2 . 39 . Each of the bottom ply boards  2 . 28 ,  2 . 31 ,  2 . 34 ,  2 . 37  are of equal length and are arranged parallel to one another and offset lengthwise from each adjacent bottom ply board  2 . 28 ,  2 . 31 ,  2 . 34 ,  2 . 37 . 
     The top ply  2 . 15  includes a first top ply board  2 . 41  having a first end  2 . 43  and a second end  2 . 45 , a second top ply board  2 . 47  having a first end  2 . 49  and a second end  2 . 51  and positioned adjacent the first top ply board  2 . 41 , a third top ply board  2 . 59  positioned adjacent the second top ply board  2 . 47  and having a first end  2 . 55  and a second end  2 . 57 , and a fourth top ply board  2 . 59  positioned adjacent the third top ply board  2 . 59  and having a first end  2 . 61  and a second end  2 . 63 . Each the top ply boards  2 . 41 ,  2 . 47 ,  2 . 53 ,  2 . 59  are of equal length and are arranged parallel to one another and offset lengthwise from each adjacent top ply board  2 . 41 ,  2 . 47 ,  2 . 53 ,  2 . 59 . 
     The bottom and top plies  2 . 13 ,  2 . 15  are attached to one another with each of the top ply boards  2 . 41 ,  2 . 47 ,  2 . 53 ,  2 . 59  extending perpendicular to each of the bottom ply boards  2 . 28 ,  2 . 31 ,  2 . 34 ,  2 . 37 , with the first end  2 . 43  of the first top ply board  2 . 41  positioned over the first end  2 . 29  of the first bottom ply board  2 . 28 , with the first end  2 . 49  of the second top ply board  2 . 47  positioned over the first end  2 . 32  of the second bottom ply board  2 . 31 , with the first end  2 . 55  of the third top ply board  2 . 53  positioned over the first bottom ply board  2 . 28 , with the first end  2 . 61  of the fourth top ply board  2 . 59  positioned over the second bottom ply board  2 . 31 , with the first end  2 . 35  of the third bottom ply board  2 . 34  positioned over the first top ply board  2 . 41 , and with the first end  2 . 38  of the fourth bottom ply board  2 . 37  positioned over the second top ply board  2 . 47 , thus forming the tabs and slots  2 . 19 ,  2 . 25  on opposite ends of each top ply board and on the opposite ends of each bottom ply board. 
     While the number and size of boards  2 . 17 ,  2 . 23  can vary depending on the size of the mat  2 . 11  desired, as hereinabove disclosed, for a mat  2 . 11  that is 12 feet (3.7 meters) long, the bottom ply  2 . 13  preferably includes a fifth bottom ply board  2 . 65 , a sixth bottom ply board  2 . 67 , a seventh bottom ply board  2 . 69 , an eight bottom ply board  2 . 71 , a ninth bottom ply board  2 . 73 , a tenth bottom ply board  2 . 75 , an eleventh bottom ply board  2 . 77 , a twelfth bottom ply board  2 . 79 , a thirteenth bottom ply board  2 . 81 , and a fourteenth bottom ply board  2 . 83 ; and the top ply  2 . 15  preferably includes a fifth top ply board  2 . 85 , a sixth top ply board  2 . 87 , a seventh top ply board  2 . 89 , an eight top ply board  2 . 91 , a ninth top ply board  2 . 93 , and a tenth top ply board  2 . 95 , with the ends of the additional top and bottom ply boards arranged in a manner like that disclosed hereinabove relative to the first four top and bottom ply boards to form the tabs and slots  2 . 19 ,  2 . 25  on opposite ends of each additional top ply board and on the opposite ends of each additional bottom ply board. 
     Left and right side versions of the mat  2 . 11  can be constructed by merely reversing the layout of the boards  2 . 23  of the top ply  2 . 15  on the boards  2 . 17  of the bottom ply  2 . 13 . Thus, the mat  2 . 11  shown FIGS. 7 and 8 can be considered a right side mat. By merely moving the boards  2 . 23  of the top ply  2 . 15  to the right one board width so that the tenth top ply board  2 . 95  is positioned over the second ends of the second, fourth, sixth, eight, tenth, twelfth and fourteenth bottom ply boards  2 . 47 ,  2 . 59 ,  2 . 67 ,  2 . 71 ,  2 . 75 ,  2 . 79 ,  2 . 83 , etc., the mat  2 . 11  can be considered a left side mat. 
     The mats  2 . 11  may be constructed in various manners and out of various materials, and in various sizes as will now be apparent to those skilled in the art. As hereinabove indicated, each of the board sections of the bottom and top plies  2 . 13 ,  2 . 15  preferably include a plurality of parallel boards. Each individual board of the bottom and top plies  2 . 13 ,  2 . 15  are preferably parallel to and the same length as all other individual boards of that ply  2 . 13 ,  2 . 15 . However, each adjacent board of each ply  2 . 13 ,  2 . 15  is offset from one another lengthwise to form the coacting, interlocking tabs  2 . 21  and slots  2 . 25 . The bottom and top plies  2 . 13 ,  2 . 15  can be built out of standard hardwood lumber using a jig or the like to insure precise placement and squareness, with the individual boards of the bottom and top plies  2 . 13 ,  2 . 15  fastened together by means of bolts, nails, glue, etc. The word “board” is used herein to define any generally long, rectangular, thin piece of wood or other substantially rigid material, composed either from a single, unitary member or a plurality of individual members, or boards, joined together, and preferably having a shear stress substantially equal to or greater than that of typical hardwood lumber, etc. 
     Description of Method of Use 
     A temporary structure such as a road or pad is constructed using a plurality of the mats of the present invention (either the mats  11  or the mats  2 . 11 ) by lifting a first mat with a forklift, crane, grapple, or other suitable equipment, and then moving that first mat into place, putting a tab end of the first mat at the starting point and putting a slotted end of the first mat in the direction of the end of the road or pad. A second mat is then lifted with the forklift, crane, grapple, or other suitable equipment, and then moved into place with the tabs of a tab end of the second mat extending into the slots of a slotted end of the first mat, with the top layer of boards being parallel or in line on both mats. This step is repeated until rows of mats of sufficient length and width are connected to build the desired road, pad, etc. If a two ply structure is not sufficient to carry the required loads on the particular ground, additional mats can be laid over the first layer of mats to reach the required mat strength (e.g.,  4  ply,  6  ply, etc.). If a three ply structure is desired, a layer of loose lumber can be laid for the bottom layer of the structure and the mats can be laid over the loose lumber. 
     As thus constructed and used, the matting system of the present invention eliminates putting down layers of matting material for the sole use of connecting the mats together, and reduces cost through less trucking and handling of the mats by laborers and equipment. The upper and lower layers of each mat are perpendicular to one another and all boards on each layer are uniformly spaced to minimize cracks and maximize strength of the mat. The slots and tabs on each mat are also uniformly spaced and of sufficient length so that every board on the top and bottom layers of the mat is overlapped by at least the length of the board&#39;s width. When a plurality of the mats are locked together using the slots&#39; and tabs, a very stable working area is provided because the slots and tabs of the surrounding mats hold each mat in place. 
     Although the present invention has been described and illustrated with respect to preferred embodiments and preferred uses therefor, it is not to be so limited since modifications and changes can be made therein which are within the full intended scope of the invention.

Summary:
A temporary support structure for use in soft and environmentally sensitive areas to construct roads and pads to support heavy equipment and the like on rough and normally impassable terrain. Roads and pads are constructed by interlocking a plurality of mats together to build a road or pad of the desired size. Each mat is comprised of two layers of boards made of a material with a shear stress equal to or greater than that of hardwood lumber. The top layer of boards are superimposed over the bottom layer and fastened by bolts, nails, glue, etc. Forklifts, cranes, etc., are used to handle individual mats and to position the mats and lock them together.