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FIELD OF THE INVENTION 
   The present invention generally relates to masonry blocks. More particularly, the present invention relates to mortarless masonry blocks that may be used to construct vertical freestanding walls or sloping walls. 
   BACKGROUND OF INVENTION 
   Mortarless masonry blocks have been known and used for many years. They are quite popular because they do not require extensive site preparation or the services of skilled craftsmen, and they are aesthetically pleasing, invoking feelings of stability, durability, and permanence. Besides being attractive and sturdy, they are generally small enough to be able to be lifted and manipulated by one person. They can range from about 6–120 pounds but more typically, though, they range around 35–70 pounds. In addition, they characteristically have only one facing or exposed face with an area in the range of about 0.17 to 1.00 square feet, and have corresponding volumes that range from about 126 to 2880 cubic inches. Such masonry blocks are commonly used to construct low retaining walls or planters, for example. 
   Most mortarless masonry blocks are manufactured using a process known in the trade as dry casting. With this process, block material having a comparatively low percentage of water (as opposed to block material that is wet cast) is deposited into an open-ended, unitary mold that is positioned on a palette and compacted by a movable piston as it moves towards the palette. Once the desired amount of compaction has been achieved, the compacted material is ejected or stripped from the mold by lifting the mold and/or moving the piston relative to the palette, or by vibrating the mold as it is moved away from the palette. The molded block is then cured outside of the mold in a series of separate steps. 
   This process allows many blocks to be manufactured in a comparatively rapid fashion because the molds are not required for the curing process. As will be understood, then, in order for these types of molds to be used most efficiently, they are usually constructed and arranged to facilitate extrusion or stripping. Most molds, therefore, comprise a vertically walled, unitary frame with no indentations or protrusions that would hinder extrusion or stripping. Blocks produced by such molds are usually symmetrically shaped so that the block may be subsequently split into two smaller, similarly shaped blocks, with each block having a substantially planar roughened facing. Alternatively, some molds may have walls with small transverse bottom ledges, or roughened divider walls, which are designed to work an uncured surface of a block as it is stripped from the mold. As will be understood, such ledges or divider walls are only capable of producing a substantially planar roughened surface, similar to the surfaces produced using the splitting technique described above. 
   A drawback with the afore-mentioned manufacturing techniques is that they are unable to produce a block that has a roughened facing that is bowed or curved with respect to the extrusion or stripping direction. If such a bowed facing is desired, the block must be worked after it has been stripped from the mold and cured, for example, by additional processing steps such as tumbling or grinding. As one may imagine, each additional processing step adds to the time and cost of the finished product. 
   A drawback with the afore-mentioned dry cast blocks is that that they are relatively small. This does not present much of a problem when retaining walls are less than 4 or 5 courses high. However, for retaining walls whose heights exceed 4 or 5 courses, it is usually necessary to provide stabilization devices to counteract the forces exerted by backfill material. Stabilization devices usually take the form of flexible sheets of a mesh-like synthetic material known in the trade as geo-grids, for example, which are usually positioned between courses of blocks and which extend horizontally and rearwardly into the backfill material that is being retained. Stabilization devices such as geo-grids may be connected to blocks by connectors, but usually they are frictionally retained in place between courses by the weight of the blocks pressing down on them. Often, it is necessary to provide stabilization devices for each course of blocks or for every other course of blocks, which adds to the cost of materials, labor, and time of construction. Unfortunately, stabilization devices can stretch, break, or be pulled out from the wall structure, which can lead to premature wall failure. 
   Another drawback common to most dry cast blocks is that they usually have only one facing or exposed face area. Thus, they are limited to a particular orientation within a structure. This limitation is underscored when the blocks are trapezoidal in shape, for example. 
   Another drawback common to most dry cast blocks is that they are designed and configured to engage vertically adjacent blocks in certain, predetermined arrangements. For example, some blocks are designed so that they can only be used to build vertical walls, while other blocks are designed so that they can only be used to build walls that have a predetermined batter or upwardly receding slope. Engagement between vertically adjacent blocks is most commonly achieved by providing blocks with integrally formed lips or protrusions that are designed to engage vertically adjacent blocks. Alternatively, engagement between vertically adjacent blocks may be achieved by providing connectors or pins that tie the blocks together. 
   Thus, there is a need for a masonry block that can be used to construct different wall structures. There is also a need for a masonry block that can be positioned in one of several predetermined orientations relative to vertically adjacent blocks to create different types of wall structures. There is also a need for a block that is able to engage vertically adjacent blocks without the use of extraneous devices or connectors. And, there is a need for a block that is capable of resisting normal forces without having to be operatively connected to stabilization devices such as geo-grids and/or earth anchors. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to masonry blocks that may be used to construct different types of wall structures. The masonry blocks have front and back surfaces, opposing side surfaces, a top surface, and a bottom surface, and are configured so that when they are arranged in a wall structure comprising multiple courses, the blocks of adjacent courses are able to interlock or engage each other so that they are better able to resist forces normal to the wall structure. 
   The top surface and bottom surfaces of each block include at least one channel and a projection, respectively. Preferably, the top surface of each block has two channels. The channels and the projection of each block are substantially linear and are aligned with each other so that they extend in the same direction relative to the block, such as across the width of the block between its opposing sides. Each channel is configured to be able to constrainingly retain one or more projections of vertically adjacent blocks to prevent forward and backward movement therebetween. The channels are arranged so that they lie adjacent the front and rear surfaces of the block, respectively, while the projection is arranged so that it lies adjacent the rear surface of the block, in vertical alignment with rearmost of the two channels. 
   The provision of the two channels and the projection allow the blocks to be used to construct different types of walls. One type of wall, for example, is a substantially vertical wall. And, within that type, different styles may be constructed. A substantially vertical wall may be constructed in which the front surfaces of all of the blocks are all on the same side of the wall, as with a running bond, for example. Such a wall will have only one side that has a substantially monolithic appearance, without large-gapped joints between adjacent blocks. 
   Alternatively, a substantially vertical wall may be constructed in which the blocks of each course of blocks are arranged in an alternating manner so that a front surface is between two rear surfaces, and a rear surface is between two front surfaces. This style of construction will result in a wall with opposing sides that appear substantially the same. That is, both sides of the wall have a substantially monolithic appearance. Another substantially vertical wall may be constructed in which a majority of blocks are positioned so that their front surfaces are on the viewable side of the wall and the remainder of the blocks are positioned in a somewhat random manner so that their rear surfaces are also on the viewable side of the wall. This style of construction will result in a wall having only one substantially monolithic appearing side. 
   Another type of wall that can be constructed using the blocks of the present invention is a sloping wall, where the wall has a predetermined batter. With this type of wall, the projections of blocks are not retained within the channels of vertically adjacent blocks. Rather, the projections are positioned so that they contact the upper margins of the rear surfaces of vertically adjacent blocks. This positions the block rearwardly with respect to the adjacent, lower block. An advantage with this type of wall structure is that it is better able to resist forces exerted by material it is retaining. Another advantage with this type of wall is that the wall may be arranged in a serpentine manner. 
   An object of the present invention is to provide a masonry block that may be used to construct a freestanding, substantially vertical wall. 
   Another object of the invention is to provide a masonry block that may be used to construct a wall having a predetermined batter or slope. 
   Yet another object of the present invention is to provide a block that has the size and bulk to be able to resist pressure exerted by retained material without having to be operatively connected to extraneous anchoring devices. 
   A feature of the present invention is that blocks in adjacent courses of blocks are able to interlock without the use of extraneous connectors. 
   Another feature of the present invention is that the block may be oriented in a variety of positions relative to adjacent blocks. 
   An advantage of the invention is that the block may be used to construct substantially vertical walls, walls having a slope or batter, walls comprising a combination of vertical and sloping portions, or serpentine walls. 
   Another advantage of the invention is that the block may be interlocked with blocks in adjacent courses of blocks without modifications or adaptors. 
   These and other objects, features and advantages of the present invention will become apparent from the following detailed description thereof taken in conjunction with the accompanying drawings, wherein like reference numerals designate like elements throughout the several views. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a preferred embodiment of the block of the present invention in juxtaposition with an averaged sized adult worker; 
       FIG. 2  is a cross-sectional view taken along lines  2 — 2  of  FIG. 1 ; 
       FIG. 3  is front elevational view of the preferred embodiment of  FIG. 1 ; 
       FIG. 4  is a top plan view of the preferred embodiment of  FIG. 1 ; 
       FIG. 5  is a cross-sectional view of a wall construction comprising a plurality of blocks arranged in substantially vertical courses; 
       FIG. 6  is a cross-sectional view of a wall construction comprising a plurality of blocks arranged in a plurality of offset courses; 
       FIG. 7  is a top plan view of a course of blocks in the wall construction of  FIG. 5 ; 
       FIG. 8  is a top plan view of a plurality of courses of blocks in the wall construction of  FIG. 6 ; 
       FIG. 9  is an alternative embodiment of  FIG. 1  of the present invention; 
       FIG. 10  is an alternative embodiment of  FIG. 1  of the present invention; 
       FIG. 11  is an alternative embodiment of  FIG. 1  of the present invention; 
       FIG. 12  is a top plan view of a course of a wall construction using the blocks of  FIG. 1 ; 
       FIG. 13  is a front elevational view of a wall construction using the blocks of the present invention, in juxtaposition with a normally sized adult worker; 
       FIG. 14  is front elevational view of a wall construction used to retain backfill. 
       FIG. 15  is side elevational view of an alternative embodiment of the block of the present invention and an open mold in which the block was cast; and, 
       FIG. 16  is a top plan view of the block of  FIG. 15  as it would be cast in a closed mold. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A preferred embodiment of a block of the present invention is depicted in  FIG. 1 . As can be seen, the block  10  is generally trapezoidally shaped and includes a front surface  12 , a rear surface  14 , a pair of opposed side surfaces  16  and  18  that extend between the front  12  and rear  14  surfaces, a top surface  20 , and a bottom surface  22 . The front surface  12 , as shown, is rough textured and substantially non-planar, and extends outwardly with respect to the front edges of the top, bottom, and opposed side surfaces. Preferably, the maximum extent or relief of the outward extension is in the range of about 2.5 to 33.3 percent of the height of the block, taken in the y direction in a three-dimensional coordinate system. The rear surface  14  is similarly textured (see, for example,  FIGS. 2 ,  4 , and  7 – 12 ) and also extends outwardly with respect to the rear edges of the top, bottom, and opposed side surfaces. As with the front surface  12 , the maximum outward extent or relief of the rear surface  14  is preferably in the range of about 2.5 to 33.3 percent of the height of the block, again taken in the y direction in a three-dimensional coordinate system. The maximum extent or relief of the outwardly extending front  12  and rear  14  surfaces is more clearly shown in  FIG. 2 . As depicted, the front and rear edges of the top  20  and bottom  22  surfaces define imaginary front  30  and rear  32  planes (shown in dashed lines), from which the maximum extents are measured. As applied to a block having a height in the range of about 18 inches, and a depth in the range of about 34 inches (as measured between the imaginary front and rear planes  30 ,  32 ), the maximum outward extent at each of the front and rear surfaces would be on the order of 0.35 to 6.00 inches, for example, and the total depth of the block could be increased from about ¾ of an inch to about 12 inches. 
   The top surface  20 , as depicted, has two channels  24  and  26  that are spaced apart from each other by a center section  28 . Preferably, both of the channels  24  and  26  are substantially linear and aligned so that they extend in the same direction, relative to the block  10 . As depicted, this is preferably in the x direction in a three-dimensional coordinate system, across the width of the block and between the opposing side surfaces  16  and  18 . The center section  28  is substantially planar and also preferably extends across the width of the block, between the opposing side surfaces  16  and  18 . 
   As depicted in  FIG. 2 , each of the channels  24 ,  26  of the top surface  20  comprises a floor  34 ,  36  and a pair of side walls  38 ,  40 , and  42 ,  44 , respectively. Preferably, the side walls  38 ,  40 , and  42 ,  44  of the channels  24  and  26  are angled away from each other so that the channels are wider at the top surface  20  than at their respective floors  34  and  36 . As will be appreciated, the angled side walls  38 ,  40 , and  42 ,  44  facilitate engagement with projections of vertically adjacent blocks, and also reduce the potential for chipping. 
   The bottom surface  22  includes a bottom section  46  and a projection  48 , with the projection comprising a base  50  and a pair of engagement surfaces  52  and  54 . Preferably, the engagement surfaces  52  and  54  are angled towards each other so that the projection tapers towards the base  50 . As with the channels, the angled engagement surfaces  52  and  54  facilitate engagement with channels of vertically adjacent blocks, and they also reduce the potential for chipping. 
   Preferably, the projection  48  is located adjacent the rear surface  14  of the block  10  so that it is in vertical alignment with the rearmost channel  26 . As with the channels, the projection  48  is also substantially linear. In addition, the projection  48  is aligned with the channels  24  and  26  such that it also extends substantially across the width of the block between the side surfaces  16  and  18 , as shown in  FIG. 3 . 
   The top surface  20  of the block  10 , as shown in  FIG. 4 , is generally trapezoidal in shape with the side surfaces  16  and  18  angled towards each other from the front  12  surface to the rear surface  14 . As will be appreciated, these angled side surfaces  16  and  18  permit the blocks to be arranged into a serpentine manner, without forming gaps between the side surfaces of adjacent blocks (see, for example,  FIG. 12 ). Preferably, the angle  56  that the side surfaces make with respect to the z direction in a three-dimensional coordinate system (see,  FIG. 1 ) is in the range of between 0 and 30 degrees, and more preferably on the order of about 6 to 23 degrees. 
   It will be appreciated that the blocks of the present invention may be arranged in a variety of different manners. For example, the blocks could be arranged so that some of the front surfaces of the blocks and some of the rear surfaces of the blocks are on the same side of the wall. This arrangement would result in a substantially vertical wall, as depicted in  FIG. 5 . Note, in  FIG. 5  that there are five courses of blocks, and that the courses are arranged in an alternating manner. More specifically, the blocks in the first C 1 , third C 3 , and fifth C 5  courses have their front surfaces showing, while the blocks in the second C 2 , and fourth C 4  courses have their rear surfaces showing. This alternating arrangement is best depicted in  FIG. 7 . Note that such an arrangement could be used to construct a wall structure that can approximate a unitary, poured wall having a minimum amount of voids. It will be appreciated that the blocks may be arranged differently, if desired. For example, the blocks could be arranged so that the front surfaces face in the same direction and the courses of blocks could be arranged in a running bond, with the projection of the upper course of blocks engaging the second, rearmost channel of the lower course of blocks. This arrangement could be used to construct a substantially vertical wall (see, for example,  FIG. 14 ). Or, the blocks may be arranged in a more random manner, so that most of the blocks have their front surfaces on the same side. It will be understood that in all of the above described vertical wall constructions, the projections will engage the channels of vertically adjacent blocks. 
   Alternatively, the front surfaces could face in the same direction, and the courses of blocks could be arranged in a running bond. However, instead of engaging the rearmost channel, with the projections of the upper course of blocks engage the upper edges of the rear surfaces of the lower course of blocks, as depicted in  FIG. 6 . This arrangement could be used to construct a wall in which courses are offset from each other, as is common in many retaining walls (see,  FIG. 8 ). 
     FIGS. 9 ,  10 , and  11  depict preferred embodiments of masonry blocks that may be used at the ends of walls. These preferred embodiments are similar to the above-described blocks in that they have a front surface, a rear surface, opposing side surfaces, a top surface, and a bottom surface. The top surface also include a pair of channels and a central section, with the channels being substantially linear and in alignment with each other between the side surfaces of the block. The bottom surface also includes a bottom section and a projection that is linearly shaped, which extends between the side surfaces, and which is in vertical alignment with the rearmost of the two channels. 
   More specifically,  FIGS. 9 ,  10 , and  11  represent three additional embodiments of different sizes of blocks that are based upon the trapezoidal block of the preferred embodiment of  FIGS. 1 ,  4 ,  8 , and  12 . The block  60  of  FIG. 9  shares some of the same dimensions as those of the trapezoidal block, namely depth and height (taken along the z and y directions in a three-dimensional coordinate system, see  FIG. 1 ). However, the front, rear, and one of the opposing side surfaces are different than the corresponding surfaces of the trapezoidal block. As depicted, the front  62  and rear  64  surfaces are substantially smaller than the front and rear surfaces of the trapezoid of  FIGS. 1 ,  4 ,  8 , and  12 . Preferably, the front surface  62  is in the range of about 20 to 50 percent of the width of the front surface  12  of a trapezoidal block, while the rear surface  64  is in the range of about 50 to 100 of the width of a rear surface  14  of a trapezoidal block. More preferably, the front surface is on the order of about 26 to 40 percent, while the rear surface is on the order of about 68 to 82 percent. As applied to a block  10  having a front  12  and rear  14  surfaces having widths in the range of around 48 and 32 inches, the widths of the front  62  and rear  64  surfaces of block  60  would be in the range of about 9.6–24.0, and 16.0–32.0 inches, for example. 
   As opposed to a generally trapezoid shape having two angled (opposing) side surfaces, block  60  has only one angled side surface  66  while the other, opposing side surface  68  is generally perpendicular to the front  62  and rear  64  surfaces. Preferably, the side surface  68 , as shown, has a roughened texture similar to the front and rear surfaces of the previously described trapezoidally shaped block. The side surface  68  also extends outwardly with respect to an imaginary plane (depicted as dashed line  70 ) extending from the front to the rear surfaces in the z direction in a three dimensional coordinate system (see,  FIG. 1 ). The maximum extent or relief of the outward extension is in the range of about 2.5 to 33.3 percent of the height of the block, taken in the x direction in a three-dimensional coordinate system (see,  FIG. 1 ). As applied to a block having a height in the range of about 18 inches, the maximum outward extend of the front and rear surfaces would be on the order of 0.35 to 6.00 inches, for example. 
   The block  80  depicted in  FIG. 10  is slightly larger than the block of  FIG. 9 , yet it is still smaller than the trapezoidal block as previously described. Preferably, the front surface  82  is in the range of about 50 to 100 percent of the width of the front surface  12  of a trapezoidal block  10 , while the rear surface  84  is in the range of about 50 to 100 of the width of a rear surface  14  of a trapezoidal block  10 . More preferably, the front surface is on the order of about 60 to 75 percent, while the rear surface is on the order of about 68 to 82 percent. As applied to a block having a front and rear surfaces having widths in the range of around 48 and 32 inches, respectively, the widths of the front  82  and rear  84  surfaces of block  80  would be in the range of about 24–48, and 16–32 inches, for example. Block  80  has only one angled side surface  86  while the other, opposing side surface  88  is generally perpendicular to the front  82  and rear  84  surfaces. Preferably, the side surface  88 , as shown, has a roughened texture similar to the front and rear surfaces of the previously described trapezoidally shaped block. The side surface  88  also extends outwardly with respect to an imaginary plane (depicted as dashed line  90 ) extending from the front to the rear surfaces in the z direction in a three dimensional coordinate system (see,  FIG. 1 ). The maximum extent or relief of the outward extension is in the range of about 2.5 to 33.3 percent of the height of the block, taken in the x direction in a three-dimensional coordinate system (see,  FIG. 1 ). As applied to a block having a height in the range of about 18 inches, the maximum outward extend of the front and rear surfaces would be on the order of 0.35 to 6.00 inches, for example. 
   The block depicted in  FIG. 11  is slightly larger than the trapezoidal block previously described. Preferably, the front surface  102  is in the range of about 70 to 100 percent of the width of the front surface  12  of a trapezoidal block  10 , while the rear surface  104  is in the range of about 125 to 175 percent of the width of a rear surface  14  of a trapezoidal block  10 . More preferably, the front surface is on the order of about 75 to 90 percent, while the rear surface is on the order of about 140 to 160 percent. As applied to a block having a front and rear surfaces having widths in the range of around 48 and 32 inches, respectively, the widths of the front  102  and rear  104  surfaces of block  100  would be in the range of about 33–48, and 40–56 inches, for example. Block  100  has only one angled side surface  106  while the other, opposing side surface  108  is generally perpendicular to the front  102  and rear  104  surfaces. Preferably, the side surface  108 , as shown, has a roughened texture similar to the front and rear surfaces of the previously described trapezoidally shaped block. The side surface  108  also extends outwardly with respect to an imaginary plane (depicted as dashed line  110 ) extending from the front to the rear surfaces in the z direction in a three dimensional coordinate system (see,  FIG. 1 ). The maximum extent or relief of the outward extension is in the range of about 2.5 to 33.3 percent of the height of the block, taken in the x direction in a three-dimensional coordinate system (see,  FIG. 1 ). As applied to a block having a height in the range of about 18 inches, the maximum outward extend of the front and rear surfaces would be on the order of 0.35 to 6.00 inches, for example. As will be appreciated, the above-described blocks enable the ends of a wall to be finished in the same manner as with the front and rear surfaces of the blocks. Thus creating a finished appearance. 
   Examples of walls constructed with the above-described blocks are depicted in  FIGS. 13 and 14 . In  FIG. 13 , W 1  is substantially vertical wall having two sides or faces and opposing ends, with the opposing ends generally parallel to each other and generally transverse to the faces of the wall W 1 . As will be noted, wall W 1  is constructed so that the interior blocks  10  are positioned in an alternating manner, while the end blocks  60 ,  80 , and  100 , are selected based so that they form a common end surface. In  FIG. 14 , wall W 2  is depicted as being used as a retaining wall. In this embodiment, most of the blocks  10  are trapezoidal and have their front surfaces facing the viewer. It will be understood that this type of wall may be either a substantially vertical wall or a sloping wall. 
   An alternative embodiment of the block of the present invention and a preferred mold are depicted in  FIGS. 15 and 16 . Referring to  FIG. 15 , the block  120  of this embodiment is generally trapezoidally shaped and includes a front surface  122 , a rear surface  124 , a pair of opposed side surfaces  126  and  128  that extend between the front  122  and rear  124  surfaces, a top surface  130 , and a bottom surface  132 . The front and rear surfaces  122  and  124 , as shown, are rough textured and extend outwardly with respect to the front edges of the top, bottom, and opposed side surfaces 
   The bottom surface  132  comprises a bottom section  140  and a plurality of projections  142 ,  144 , with each projection comprising a base and a pair of engagement surfaces. Preferably, the engagement surfaces of each projection are angled towards each other so that the projection tapers towards the base (see,  FIG. 16 ). Preferably, the projections  142 ,  144  are located adjacent the rear surface  124  of the block  120  so that they are in vertical alignment with the rearmost channel  136  (see,  FIG. 16 ). As can be seen, the projections  142 ,  144  are aligned in the x direction of a three-dimensional coordinate system across the width of the block  120  between the side surfaces  126  and  128  (compare with  FIG. 1 ). Since the weight of the block  120  may become quite large and unmanageable, even for a skid-steer loader, one or more cores can be used to reduce the weight without reducing the overall dimensions of the block. Such a core can be used advantageously at the bottom section  140  to produce a core hole  146 , for example. This can allow more blocks to be loaded onto a transport, which saves time and money. 
   The top surface  130 , as depicted from the side in  FIG. 16 , has two channels  134  and  136  that are spaced apart from each other by a center section  138 . Preferably, both of the channels  134  and  136  are substantially linear and aligned so that they extend in the same direction, relative to the block  120 . This is preferably in the x direction in a three-dimensional coordinate system, across the width of the block and between the opposing side surfaces  126  and  128  (compare with  FIG. 1 ). The center section  138  is substantially planar and also preferably extends across the width of the block  120 , between the opposing side surfaces  126  and  128 . Optionally, the center section may be provided with a cylindrically shaped indentation  148  with a transverse or axial rod or wire  149 , which forms a lifting point for the block  120 . 
   While it will be appreciated that different methods and processes may be used to manufacture the aforementioned block embodiments, the inventor has discovered that the larger sized blocks are best suited for manufacture using the wet casting process. Moreover, it has been discovered that dimensional accuracy and consistency can be more easily achieved if the blocks are cast on their sides so that the front and rear surfaces are vertical.  FIG. 15  depicts a block  120  that is being removed from mold  150 . As shown, the bottom or base  152  of the mold is positioned on a support “S” so that the side surface  126  of the block is more or less horizontal. Side walls  154  and  156 , having textured surfaces  166 ,  168 , and which are removably attached to the base  152  by pivot pins  162  and  164 , have been unlatched from the other similarly attached side walls  158  and  160  (see,  FIG. 16 ) of the mold  150  and swung away from contact with the block surfaces  124 ,  126 . In this position, the block is now ready for removal from the mold. As will be understood, the side walls of the mold are attached to each other by latches  170 ,  172 ,  174 ,  176 , in a conventional manner. 
   An advantage to forming the block on its side is that it ensures that the mold material is disbursed evenly along the channels and along the front and rear surfaces. In addition, it is easier to form the block such that the distance between the top and bottom surfaces is consistent and within manufacturing specifications. With the preferred method of casting, only one side of the block need be hand finished. And, as will be appreciated, this will not appreciably affect wall construction. 
   While preferred embodiments of the present invention have been shown and described, it should be understood that various changes, adaptations, and modifications may be made therein without departing from the spirit of the invention. Changes may be made in details, particularly in matters of shape, size, material, and arrangement of parts without exceeding the scope of the invention. Accordingly, the scope of the invention is as defined in the language of the appended claims.

Summary:
A block used to construct a wall. The block has a front and rear surfaces, top and bottom surfaces, and side surfaces. The bottom surface of the block has a projection that extends downwardly therefrom and which is configured to engage one or more blocks in an adjacent course of blocks to prevent movement therebetween. Depending upon the configuration of the wall, the projection may engage a portion of the rear surface of an adjacent course of blocks, or may be received within one of two channels in the top surface of the adjacent course of blocks. By selecting the position of the projection relative to the adjacent course of blocks, differently configured walls may be constructed.