Patent Publication Number: US-6666625-B2

Title: Retaining wall support posts

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of patent application Ser. No. 09/650,982 filed Aug. 30, 2000, now abandoned. 
    
    
     TECHNICAL FIELD 
     This invention concerns garden landscaping. More particularly, it concerns support posts for use in the construction of retaining walls and/or fences used in garden landscaping. 
     BACKGROUND OF THE INVENTION 
     Conventional practice in garden landscaping when erecting retaining walls is to construct the retaining wall or walls using bricks, or stones, and mortar. If the retaining wall does more than simply form the edge of a garden bed, it is an inherently expensive structure and takes a considerable time to erect. Consequently, large retaining walls are usually permanent garden structures. 
     To facilitate the construction of such large retaining walls, special bricks or blocks have been proposed. Recent examples of such bricks or blocks are described in the specification of the U.S. Pat. No. 5,456,555 (angular building blocks); in WIPO Publication No. WO 95/23897 (the specification of International patent application No. PCT/US95/02543-modular wall block system); and in the specification of Australian patent No. 665,923 (interlocking bricks). 
     Large retaining walls are also constructed using heavy timber. In Australia, treated logs and so-called “railway sleepers” have been used in garden landscaping. The specification of Australian patent application No. 27444/92 describes landscaping logs adapted to be combined together and fastened to each other to form a retaining wall structure. 
     Another type of large retaining wall is constructed using boards, panel members, planks or the like positioned between specially shaped posts. For example, posts having a T cross-section are erected along the required line of the retaining wall with the top arm of the “T” aligned with the wall direction and the vertical arm of the “T” at a right angle to the wall direction. Planks, panels, and even logs may then be positioned with their ends abutting (or nearly abutting) the inwardly directed arms of the T-section posts to form a wall. Such retaining wall constructions are featured in, for example, 
     (a) the specification of Australian patent application No. 12612/88 (in which the T-section posts are provided with an elongated base and a vertical plate, to enable earth or other fill to stabilise the frames formed with the T-section posts); 
     (b) WIPO Publication No. WO 95/13431 (the specification of International patent application No. PCT/AU94/00692, in which the T-section posts are constructed using T-section modular units, with varying lengths of the “vertical” arm of the “T”, and are restrained by a footing and a “deadman” anchor arrangement); and 
     (c) WIPO Publication No. WO 84/04768 (the specification of International patent application No. PCT/US84/00781, in which concrete T-posts are assembled with post-tensioning devices and the stability of the retaining wall is achieved with base members onto which soil or other fill is placed). 
     A similar retaining wall construction uses posts which include a channel member each side of the post. A number of these posts are erected along the required line of the retaining wall. Panel members, planks or the like, each having a length essentially the same as the distance between adjacent posts of the wall, are then mounted with their ends inside the facing channels of adjacent posts. Suitable bracing or anchoring means are provided, then soil or other fill is placed behind the panels or planks. Examples of such constructions are described in the following documents: 
     1. The specification of U.S. Pat. No. 5,671,584, to John F Mueller. This specification discloses the use of “H-beam” post members, which are post members specially constructed to have a central cavity so that the post members can be placed over respective stakes which have been driven into the ground along the required line of the retaining wall. There is a channel on each side of the “H-beam” post. A retaining wall is constructed by sliding the ends of a plank into the facing channels of adjacent “H-beam” posts, then repeating this procedure with additional planks. If necessary, anchors connected by cables to holes in the “H-beam” posts are used to ensure that the retaining wall remains upright after back-filling. 
     2. The specification of Australian patent application No. 54785/96, by M. Vincentini and G. Belladonna. This specification discloses a retaining wall constructed by sliding panel members into channels—grooves—in upright post members formed by folding lengths of sheet metal. 
     3. WIPO Publication No. WO 99/20846 (the specification of International patent application No. PCT/CA98/00961 by Durisol, Inc.). This document describes the construction of a retaining wall with posts that have channels formed by two flanges connected by a web, which are held in position by anchors that are similar to the anchor of Mueller&#39;s retaining wall—see the aforementioned specification of U.S. Pat. No. 5,671,584. 
     4. The specification of Australian patent application No. 81448/75, which describes a sea retaining wall formed using panels—baffle elements—which are inserted into the channels of a series of I-beams that have been driven into the earth, with a series of “earth weight anchoring support elements” extending rearwardly from the baffle elements. 
     5. The specification of Australian patent No. 697,901, to Armstrong &amp; McGovern Limited of New Zealand. This specification discloses how sheet metal panels are progressively lowered into the grooves of adjacent piles, to form a retaining wall, as the region in front of the retaining wall is excavated. 
     6. The specification of U.S. Pat. No. 3,193,255 of H. D. Burdett, which describes a channelled post and plank system, to form a fence. 
     DISCLOSURE OF THE PRESENT INVENTION 
     The first paragraph of the aforementioned specification of Australian patent application No. 81448/75, filed in May 1975, begins: 
     “Prior to the present invention, there have existed numerous complicated and impractical sorts of retaining walls from the standpoint of required strength and durability while concurrently being of simple structure . . . that may be mass produced and shipped and assembled on site, with a minimum of experience . . . ” 
     That statement could well begin the present specification, as a reference to retaining walls used in garden landscaping today. 
     It is an objective of the present invention to provide a support post for a retaining wall which enables the retaining wall to be constructed more economically, in a significantly shorter time, and with the facility to remove the retaining wall without difficulty or to change the position of the retaining wall should a revised garden landscape be required in the future. 
     It should be noted that in this specification, including the claims, the terms “upper”, “lower”, “top”, “bottom”, “vertical”, and other “directional” terms, will be used in the sense that these terms will have when the invention is used in the construction of a retaining wall. In addition, the term “wall member” will mean a generally elongate member, preferably of substantially uniform width, such as a plank or beam (typically, but not necessarily, of wood), having, at least at each end thereof, a flat face, the plane of each flat face being orthogonal to the elongate direction of the member. 
     The above-mentioned objective is achieved by providing a support post in the form of a plate member which has at least one hole in it through which a bolt, screw or heavy gauge nail can pass to hold a wall member firmly against the plate member. The plate member is pointed at its lower end so that it can be driven into the ground a distance which is sufficient to ensure that the post, when free-standing, will be a rigid and substantially vertical support for the wall member or wall members. The plate member may be formed with at least one stiffening or reinforcing feature, which may be a length of metal rod or angle iron, or may be a fold or ridge, extending the length of the plate member. A spike extending below the point of the plate may be provided, to assist (a) in the penetration of the ground, and (b) in ensuring that the support post is substantially vertical. If such a spike is present, it may be formed integrally with the plate member or it may be bonded to the plate member (for example, by welding). 
     Thus, according to the present invention, a support post for use in the construction of a retaining wall comprises, in its broadest form, a single rigid, elongate plate member, having a top edge, two side edges and a bottom edge, characterised in that 
     (a) said bottom edge is pointed; 
     (b) said plate member has a lower plate portion which, when said support post is in use in the construction of a retaining wall, is inserted into the ground; 
     (c) said plate member has an upper plate portion, extending from the top of said lower plate portion to said top edge, said upper plate portion, when said support post is in use in the construction of a wall, being positioned adjacent to a wall member of said retaining wall; and 
     (d) at least one aperture is provided in said upper plate portion, through which a respective securing means (for example, a bolt, screw or the like) may be passed to secure a wall member of said retaining wall to said plate member. 
     The point (which may be a chisel point) of the bottom edge may be extended downwardly to form a spike. 
     Normally, the support post will be symmetrical about an imaginary vertical line extending from the centre of the top edge through the point of the bottom edge, and the side edges will be substantially parallel to each other or downwardly slightly divergent or convergent. However, for decorative purposes, the side edges may be non-linear, and may be smoothly shaped so that it is not always possible to observe where the upper edge of the plate member ends and each side edge begins. 
     When intended for use at a corner of a retaining wall, the plate of the support post may be non-planar. In this configuration, the plate member will normally comprise two substantially identical “half-plates”, each extending from the vertical line of symmetry of the support post. The included angle between the half-plates of the support post need not be a right angle, but should be a right angle when the support post is to be used at a right-angled corner of a retaining wall. 
     A rod-like extension of the support post above its top edge may be provided. When the support post is symmetrical about a vertical line of symmetry, the rod-like extension will be substantially colinear with the vertical line of symmetry. Such an extension will normally have one or more grooves, or holes, in it, for use in locating a wire, cable or hose that is to be positioned above the retaining wall. Alternatively, the extension may terminate in a threaded boss. 
     In one embodiment of the support post of the present invention, the plate member is attached to a vertical rod along the vertical line of symmetry. In another realisation of the present invention, two separate “half-plates” are welded to a vertical rod. In these forms of the present invention, the vertical rod will normally extend below the point of the bottom edge of the support post to provide the aforementioned spike, and will be independently pointed at its lowermost end. The rod may also extend upwardly above the top edge of the support post. 
     If the plate member is roll formed from steel plate, it is preferably formed with a central vertical fold or ridge, to provide extra stiffness to the plate member. A short cylinder may be welded within the ridge or fold, at the top of it to facilitate driving the lower portion of the plate member into the ground. Alternatively, a vertical rod may be positioned (and welded) within the ridge or fold, with an extension below the bottom edge of the plate member, to form a spike. 
     Several embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
     FIG. 1 is a perspective sketch of the most basic support post of the present invention. 
     FIG. 2 is a perspective sketch of another basic support post of this invention. 
     FIG. 3 is a perspective sketch of a modified form of the support post illustrated in FIG.  2 . 
     FIG. 4 is a perspective sketch of another support post constructed in accordance with the present invention, having a roll formed plate member. 
     FIG. 5 is a top view of the support post illustrated in FIG.  4 . 
     FIG. 6 is a front view of another modified form of the support post illustrated in FIG.  2 . 
     FIG. 7 is a perspective sketch of a different construction of a support post having similar features to the support post of FIG.  6 . 
     FIG. 8 depicts an alternative construction of a support post having similar features to the support post of FIG.  7 . 
     FIG. 9 is a sectional view through a portion of a retaining wall constructed using the support post illustrated in FIG.  8 . 
     FIG. 10 is a vertical section view through another form of the support post constructed in accordance with the present invention. 
     FIG. 11 is a vertical section through part of a modified form of the support post shown in FIG.  10 . 
     FIGS. 12 and 13 are sectional views through tools which may be used when support posts as illustrated in FIGS. 10 and 11 above are driven into the ground. 
     FIG. 14 is a top view (similar to FIG. 5) of a modified form of the support post depicted in FIGS. 4 and 5. 
     FIG. 15 depicts a corner of retaining wall which has been constructed using a corner support post in accordance with the present invention. 
     FIG. 16 is a sketch of a corner of a retaining wall with a mesh fence above it, constructed using a corner support post in accordance with the present invention. 
     FIG. 17 shows a support post construction which may be used at an end of a retaining wall. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     FIGS. 1 and 2 each depict a simple support post consisting of a steel (or other suitable material) plate member  10 . The plate member  10  has a top edge  11 , side edges  12  and  13 , and a bottom edge in two parts  14 A and  14 B, which meet at a point  15 . The plate member  10  contains one hole or aperture  16  (FIG. 1) or one pair of holes or apertures  16  (FIG.  2 ). The holes  16  in the embodiment illustrated in FIG. 2 are equidistant from the upper edge  11 ; they are also equidistant from the point  15  and, consequently, they are equidistant from the vertical line of symmetry  20  of the plate member  10 . 
     The plate members shown in FIGS. 1 and 2 are intended to be used in the construction of a low retaining wall comprising a single plank of wood. (A retaining wall of this construction is suitable for use as the edge of a flower bed.) The plate member  10  is driven into the ground a distance d. The distance d is the distance between two imaginary lines AA and BB. The portion of the plate member  10  which is above the line AA constitutes an upper plate portion  19 A. The portion of the plate member  10  which is between the lines AA and BB constitutes a lower plate portion  19 B. 
     When the lower plate portion  19 B of the plate member of FIG. 1 has been driven into the ground, a plank of wood may be placed against one of the flat surfaces of the upper plate portion  19 A. When the lower plate portion  19 B of the plate member  10  of FIG. 2 has been driven into the ground, the ends of two planks of wood can be aligned adjacent to the upper plate portion  19 A with abutting ends positioned substantially at the vertical line of symmetry  20 . A respective screw, bolt, nail or other suitable securing means can then be passed through the, or each, hole  16  and into (or through) the adjacent plank or plank end, to hold the plank or plank ends in contact with the plate  10 . When the plank or the other ends of the planks have been suitably supported elsewhere, soil (or other fill, such as gravel, or chips, or stones, or mulch) can be deposited to a depth up to the width of the plank or planks. 
     The support post shown in FIG. 3 is a modified form of the support post illustrated in FIG.  2 . The embodiment of FIG. 3, when intended for the construction of a low retaining wall at the edge of a flower bed, may be made from a high density plastic material (for example, a polycarbonate material) or it can be roll formed from steel sheet. It contains two ridges or folds  50 ,  51 , which act as stiffening or strengthening ribs which prevent unwanted flexing of the plate member. The ridges  50 ,  51  need not be at the side edges of the plate member; they can be nearer to the vertical line of symmetry of the plate member. In fact, they can be replaced with a single, central ridge or fold at the vertical line of symmetry, as in the embodiment illustrated in FIGS. 4 and 5. 
     The plate member of the support post of FIGS. 4 and 5 will normally be made from steel plate by a roll forming process. This embodiment has a single vertical ridge or fold  52  and the regions  53  and  54  of the plate member which are adjacent to the side edges are folded to provide further stiffening. It is intended for use when the retaining wall to be built is somewhat higher than that which can be constructed using a support post shown in FIGS. 1,  2  and  3 . 
     The ridge or fold  52  is shown as generally V-shaped in cross-section, for this shape is believed to be a convenient shape to produce with a roll forming operation. However, ridges which are U-shaped, or semi-circular in cross-section, or which have a cross-section that is three sides of a rectangle, are among the alternative shapes for this feature. A solid steel cylinder (or a length of pipe forming an open-ended cylinder)  55  is welded into the fold or ridge  52 , with the end  56  of the cylinder or pipe  55  substantially coplanar with the top edge  11  of the plate member. With this arrangement, a hammer impacting on the top of the ridge  52  and also on the end  56  of the cylinder (or length of pipe)  55  can be used to drive the bottom edge of the plate member into the ground without risk of damage to the top edge of the plate member. 
     The support post illustrated in FIG. 6 is constructed from a single piece of steel plate or other suitable material. This support post is also intended for use when the retaining wall to be built is somewhat higher than that which can be constructed using a support post as shown in FIG. 1,  2  or  3 . In addition to being a taller support post, with several pairs of holes or apertures  16 , the plate member  10  of FIG. 3 has a downwards extension from the point  15  to form a spike  17 , which terminates in a point  18 . It should be apparent that, depending on the width of the planks, two or three planks (or alternative form of wall member) of a retaining wall can be supported on each half of the support post, with the respective opposed ends of each plank (or other wall member) abutting at the vertical line of symmetry  20  of the plate member. 
     FIG. 6 also shows, in dashed outline, a rod-like upward extension  22 . The extension  22 , if appropriately grooved, or with at least one hole drilled through it, can be used to support a wire, a cable or a hose above the retaining wall, as will be explained in more detail later in this specification. A length of angle iron or metal rod (not shown in FIG. 6) may be welded to the plate member (for example, along the vertical line of symmetry of the plate member) to prevent flexing of the plate member when the support post is used in a retaining wall. 
     The support post illustrated in FIG. 7 has a plate member similar to (but taller than) that shown in FIGS. 1 and 2, with a metal rod  23  of rectangular cross-section welded to it, along the vertical line of symmetry  20  of the plate member. The rod  23  extends below the point  15  of the plate member  10  to form a spike  17  with its point  18 . 
     The support post shown in FIG. 8 has two “half-plates”  10 A and  10 B welded to diametrically opposed regions of a steel rod  24  of circular cross-section, the rod  24  extends below the point at the junction of the lower edges  14 A and  14 B of the half-plates  10 A and  10 B, to form a spike  17  with its own point  18 . 
     FIG. 9 illustrates a typical retaining wall structure, created using planks  30  and  31  supported by a support post constructed as shown in FIG.  8 . After driving the lower plate portion  19 B of the support post into the ground the required distance d, the planks  30  and  31  are positioned adjacent to the half-plates  10 A and  10 B with the ends of the planks abutting (or almost abutting) each other. A chamfer on the end of each plank may be required to enable the ends of the planks to abut against each other and then be held firmly against the respective faces of their respective adjacent half-plates  10 A and  10 B using bolts  25  (which pass through the planks and the holes or apertures  16  in the half-plates) and nuts  26 . When soil or other fill  33  is deposited behind the retaining wall, the support plate will not be readily visible, as one face of each half-plate is covered by the soil  33  and the other face of each half-plate is covered by the abutting ends of the planks  30  and  31 . 
     In some gardens, it may be desirable to support a wire (or more than one wire) above a retaining wall. Alternatively, or in addition, it may be advantageous to support a hose of a watering system, or an electrical cable (for lighting the garden) above a retaining wall. For this purpose, the support post of the present invention may be constructed with an integral rod-like upward extension, as suggested in the description of the embodiment illustrated in FIG. 6 of the accompanying drawings. Another support post with an upward rod-like extension is shown in FIG.  10 . In the FIG. 10 embodiment, two half-plates  10 A and  10 B are welded to a central steel rod  24  which has a lower spike portion  17  and an upper extension  34 , with apertures or holes  35  drilled through it. In a modified form of the support post shown in FIG. 10, the apertures  35  are replaced with grooves or slots, appropriately dimensioned. A wire, cable or hole may be passed through an aperture  35 , if the aperture is appropriately dimensioned, or a known support means for a wire, cable or hole may be attached to the aperture  35  or an alternative groove or slot. 
     FIG. 11 depicts the top of the upper plate portion of the embodiment illustrated in FIG. 7, but with a short extension  34  to which a boss  36  is affixed. The boss  36  has an internally threaded bore or cavity  37  into which the threaded lower end of a post  38  may be screwed. The post  38  may be a fence-post (for example, a post used in the construction of a swimming pool fence). 
     A metal rod having a length which is longer than the plate member, and having a cross-section that enables it to be fitted into the groove or ridge  52 , may replace the cylinder or length of pipe  55  of the support post shown in FIGS. 4 and 5, to produce another realisation of a support post with a spike extending below the junction of the lower edges of the plate member. Such a metal rod may also extend vertically above the top edge  11  of the roll-formed plate member  10  of the embodiment of FIGS. 4 and 5, in which case the metal rod may be provided with support means for a wire, a cable, a hose or a post, similar to the support means featured in the embodiments of FIGS. 10 and 11. 
     To drive the support post shown in FIGS. 6 (with the extension  22 ),  10  and  11  into the ground without risk of damage to the upwards extension above the plate member of the support post, a generally cylindrical protective sleeve  40 , as shown in FIG. 12, may be used. The sleeve  40  has a cylindrical body  41 , a closed top  42  and an annular foot member  43 . Typically the body  41 , top  42  and foot member  43  will be of steel, and will be welded together to form a rigid sleeve  40 . In use, the sleeve  40  is placed over the extension  34  with the foot member  42  resting on the top edge  11  (actually, two half-edges  11 ) of the half-plates  10 A and  10 B and with the top  42  clear of the top of the extension  22  or  34 . By striking the top  42  of the protective sleeve, impact pressure is applied to the half-plates  10 A and  10 B and the support post is driven into the ground. 
     An alternative tool for driving the lower plate portions of the support posts shown in FIGS. 6,  10  and  11  into the ground is illustrated in FIG.  13 . This alternative tool comprises a cylindrical foot member  47  having an annular cross-section, with a pair of diametrically opposed arms  48  welded to or formed integrally with the foot member  47 . With the foot member  47  surrounding the extension  22  or  34 , this tool may be moved manually so that the foot member  47  impacts on the top edge (or half-edges)  11  to drive the support post into the ground. 
     A landscape gardener may be asked to construct a retaining wall which has a corner (or more than one corner) in it. If that is the case, and the wall is to be constructed using the present invention, it will be desirable to have a support post at the (or each) corner of the retaining wall. For this purpose, the support post of FIGS. 4 and 5, modified as shown in FIG. 14, may be used. The support post shown in FIG. 8, with appropriate modification, can also be used to produce a corner support post for a retaining wall. Such a corner support post, with planks  30 A,  30 B,  31 A and  31 B of a retaining wall, is featured in FIG. 15 of the accompanying drawings. 
     It should be apparent that the support post shown in FIG. 15 has two half-plates  10 A and  10 B which are not coplanar, but are welded to a “central” rod  24  so that they include an angle of approximately 90°. It should also be apparent that it is a straightforward task to make a support post for a retaining wall with any required included angle by welding two half-plates to a metal rod. 
     A basic form of a support post for use at a corner of a low retaining wall is a support post similar to that shown in FIG. 2, with the plate member  10  bent about the vertical line of symmetry  20 , to form two half-plates with the required included angle for the corner. 
     FIG. 16 of the accompanying drawings is a sketch showing a corner of a retaining wall constructed using another form of support post which is also in accordance with the present invention. This support post has decorative half-plates  10 A and  10 B welded to a single steel rod  24 , with an upwards extension  34 . Holes or grooves in the extension  34  support two wires  45 , which in turn support a strip of wire mesh  44 . The retaining wall in FIG. 16 comprises a double layer of treated pine planks  30 A,  30 B,  31 A and  31 B. 
     If there is a rock feature, a tree stump, a lamp standard or some other object at or very close to one end of a retaining wall, the retaining wall may terminate without turning a corner. In such a situation, the support post shown in FIG. 17 may be used at a termination of the retaining wall. This support post, which does not have a vertical line of symmetry, comprises a plate member  10  welded to a steel rod  24 . The bottom edge  14  of the plate member  10  forms a chisel point  15  with the side edge  12  of the plate member. The rod  24  extends downwards as a spike  17  with a pointed end  18 . Optionally, the rod  24  may extend above the top edge  11  of the plate member  10 . This optional extension  34  may terminate in a boss  36  having an internally threaded cavity to receive the threaded lower end of a fence post. Another optional feature of the support post shown in FIG. 13 is an end plate member  49 , welded to the rod  24  so that the planar faces of the end plate member  49  are at right angles to the planes of the faces of the plate member  10 . The end plate member  49 , if present, covers the end faces of the planks or other wall members that are fixed to the plate member  10 . 
     It will be apparent from the above description of the illustrated embodiments that the preferred material for construction of the support post of this invention is steel. Initial experiments have shown that the plate member (or the half-plates) of the embodiments illustrated in FIGS. 1,  2 ,  6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  15 ,  16  and  17  may conveniently be 5 mm thick mild steel plate, and if the support post has a spike, the spike  17  should have a length of about 100 mm. In addition, to avoid the need for bracing members or anchors attached to the support posts, the steel plate at the level where the upper plate portion meets the lower plate portion should be at least 100 mm wide. In the constructions using a rod  24  of circular cross-section, the rod should be a solid rod of diameter 20 mm. If the support posts of the present invention are used to construct a retaining wall which is more than 300 mm high, the distance d between the point  15  of the plate member (or the half-plates) of the support post and the surface of the ground, when the support post has been driven into position, should be about 300 mm. However, it should be noted that other materials may be used for the support posts of the present invention and other dimensions of parameters of the post embodiments may be adopted, provided the final product support post is effective to support the retaining wall members safely. Included in the other materials that may be used to make the support posts of this invention are a number of aluminium alloys, steel sheet (see the embodiment of FIGS. 3,  4 ,  5  and  14 ), other types of steel, other suitable metals and alloys, and (particularly if a low level retaining wall is to be constructed) high density plastic materials (such as polycarbonates) and wood (either hardwood or treated to prevent rotting). This list is not exhaustive. If a plastic material is used, as noted above, the plate member or half-plates will normally be moulded to include strengthening ribs. 
     Although treated pine planks are the inventor&#39;s preferred wall members for use with the support posts of this invention, other wall members may be used to construct a retaining wall. The other wall members include hardwood planks, treated pine logs with their ends shaped to provide at least one flat face which may be secured against a face of a plate member, lengths of sheet metal and lengths of metal decking. This list, also, is not exhaustive. 
     To protect the wall members of a retaining wall, an elongate, channel-shaped “cap” or cover may be placed over the top wall member. In addition, if steel is used for the present invention, it will be advantageous to coat the support post—or at least the lower plate portion of the support post that will enter the ground—with black tar or another rust-inhibiting compound. 
     Engineers, gardeners and landscape architects will appreciate that the present invention is not limited to the embodiments illustrated and described in this specification, and that modifications of and variations to the illustrated embodiments may be made without departing from the present inventive concept, as defined by the following claims.