to provide an understanding of certain terms used in the specification and claims of this application , the following definitions are set forth : system module -- the nominal size ( length and width ) of each access floor panel unit ; also the nominal spacing of access floor panel supporting members laterally and longitudinally ; also the nominal size ( length and width ) of each modular tile . modular tile -- a floor covering unit nominally equivalent in size to the system module . on - module -- the location of each modular tile directly on top of each individual access floor panel with no overlap . off - module -- the location of a modular tile , offset from the system module by 1 / 2 module , such that each modular tile will cover the four adjacent quarters of four adjacent panels . indexing tool or fixture -- a separate tool made to position the floor covering to a pre - determined location relative to the floor panel module , so that the two units can be assembled on module . tile -- a secton of any of a number of floor covering materials such as : ( but not limited to ) carpet resilient tile , i . e . rubber , vinyl , cork , linoleum wood parguetry , wood strip , plywood , hpl ceramic tile , marble , terra cotta , terrazzo artificial glass . substantially of the same size -- dimensionally nearly identical to a referred object within manufacturing tolerances acceptable within the industry and , in the present case , such tolerance is within 0 . 5 % of each dimension ( length and width ) of each modular tile . hole -- an opening , recess , groove or similar aperture or indentation allowing for reception of a cooperative projection therewithin . projection -- an element raised from the upper or lower surface of a tile or panel for cooperation with a corresponding hole . position modularity -- a dimensional relationship between a tile and a corresponding panel or group of panels which allows for interchangeability of said tile with any other panel so as to provide a predetermined acceptable fit with one another . referring initially to fig1 shown therein is a perspective view , partially exploded , illustrating a modular tile 1 which is operatively associated with an access floor panel 2 made of , for example , steel or plastic . as shown in fig1 the series of access floor panels 2 form an access floor panel system upon which is mounted one or more tiles 1 . reference number 3 indicates a top surface portion of each access floor panel 2 while reference number 4 indicates at least one projection extending downwardly from a bottom surface portion 28 of the tile 1 . reference number 5 denotes an edge flange of each access floor panel 2 . each tile can be provided with an optional projection 6 for directional control and orientation of the tile 1 with respect to each access floor panel 2 . reference number 7 indicates the side wall of each access floor panel 2 while reference number 8 indicates a magnetic or pressure sensitive adhesive perimeter of each tile 1 which also is optional and which serves to prevent lifting or curling of the tile 1 along the edge portion or perimeter 9 thereof or at a corner 11 thereof such that each tile 1 is removable and replaceable without the use of indexing tools or fixtures . reference number 10 indicates a positioning hole for on module installation . upon engagement of tile 1 with one or more respective access floor panels 2 , the projections 4 in each tile 1 serve to position , index and maintain position modularity of the tile 1 relative to the access floor panel system . the projections 4 cooperating with the positioning holes 10 are of corresponding configuration so as to orient each tile 1 to each of the panels 2 such that each tile is removable and replaceable without the use of indexing tools or fixtures and such that each tile is substantially of panel module size . it is important to note that , in accordance with the invention , the modularity of the panels 2 and also the tiles 1 are dimensionally consistent such that each tile can be relocated on any other panel so as to maintain a consistent modular interface . as can be appreciated from a review of fig1 it is possible for a single projection 4 from each tile 1 to serve as a positioning and indexing means which indexes into only one positioning hole 10 formed in each of the floor panels 2 due to engagement of adjacent edge portions or perimeters 14 of each tile upon being mounted on two or more adjacent access floor panels 2 . an adjustable pedestal 22 in combination with a support platform 24 serves to support each of the access floor panels 2 from a floor in a conventional manner . the manner of use of the adjustable pedestal 22 and support platform 24 are apparent from a review of fig1 - 3 . fig2 serves to illustrate a view similar to that of fig1 but showing an alternative arrangement of tiles 1 on the access floor panels 2 . more particularly , while the arrangement of projections 4 on the bottom surface portion 28 of each tile 1 is the same as that as shown in fig1 the arrangement of the positioning holes 10 differs from that of fig1 insofar as the positioning holes are located in a central portion of each access floor panel 2 so as to allow for overlapping of a single tile 1 onto adjacent quarter sections of four panels . otherwise , the embodiment shown in fig2 directly corresponds to the structural element shown in fig1 . fig3 again relates to a vertical cross - sectional view taken on lines iii -- iii of fig2 and serves to more clearly illustrate the manner in which the panels 2 are supported by pedestal 22 and support platform 24 as well as the cooperative engagement of edge portion or perimeter 9 of each panel and the cooperative engagement of edge portion or perimeter 14 of each tile 1 . next referring to fig4 such illustrates an exploded vertical cross - sectional view showing in greater detail the structure of tile 1 and access floor panel 2 . more particularly , reference number 15 denotes a carpet pile or similar surface such as , for example , a vinyl surface , an asbestos surface , a rubber surface or a similar type of surface found to be acceptable in the floor covering industry . reference number 16 serves to indicate a primary backing of carpet pile 15 while reference number 18 denotes an adhesive bond for the carpet primary backing 16 . a backing structure 19 is utilized to serve as a further backing for the primary backing 16 wherein the projections 4 are integral with and extend from the plane of backing structure 19 for indexing into positioning hole 10 formed in access floor panel 2 . backing structure 19 therefore serves to engage top surface portion 3 of access floor panel 2 . fig5 shows an alternate embodiment of the structure of fig4 wherein the projection 4 extending from backing structure 19 is formed with undercut snaps 20 for a more secure engagement with positioning hole 10 to prevent uplift . fig6 shows yet another alternate embodiment of the structure of fig4 which utilizes a conductor 21 in the form of a backing . as seen in fig6 projection 4 extends through a hole 23 formed in backing structure 19 and also cooperates with projection hole 10 formed in floor panel 2 . accordingly , projection 4 extending from conductor 21 also serves to position , index and maintain the position of the tile 1 relative to the access floor panel 2 wherein projection 4 and conductor 21 are made of a conductive material for providing improved resistance to static electricity build - up on the surface of the tile while also being of a configuration which orients the tile 1 to each of the panels 2 such that the tile 1 is removable and replaceable without the use of the aforementioned indexing tools or fixtures . fig7 a - 7e serve to illustrate yet another embodiment of the present invention wherein fig7 a illustrates an underside perspective view of the tile 1 while fig7 b shows a vertical cross - sectional fragmentary view taken along line b -- b of fig7 a . these figures serve to illustrate a rim projection 26 extending downwardly along the periphery of the tile 1 such that bottom portion 28 is completely surrounded by rim projection 26 . fig7 c illustrates a top view of the floor panel 2 associated with the tile 1 of fig7 a while fig7 d illustrates a vertical cross - sectional view on line c -- c of fig7 c . in these figures , reference number 30 indicates a hole or recess formed in the periphery of floor panel 2 while reference number 32 indicates an offset panel top surface . fig7 e sets forth a vertical cross - sectional view showing engagement of rim projection 26 with offset panel top surface 32 and which therefore serves to position , index , and maintain position modularity of the tile 1 relative to the access floor panel 2 so that again , tile 1 is removable and replaceable without the use of indexing tools or fixtures and the tile is substantially of the panel module size . also again in this embodiment , the modularity of the panel 2 is dimensionally consistent such that the tile 1 can be relocated on any of a number of panels 2 so as to maintain a consistent modular interface . fig7 f illustrates a vertical cross - sectional view of a variation on the embodiment of fig7 e wherein an offset tile lower surface 33 is used and which is cooperatively engageable with a rim projection 35 in the top surface of panel 2 . the features of this embodiment are otherwise identical structurally and functionally to that of the embodiment in fig7 e . therefore , in the embodiment of fig7 e , each of the panels 2 has at least one positioning offset 32 formed along the periphery thereof as well as rim projection 26 extending from and along the periphery of tile 1 which indexes in the positioning offset 32 . in fig7 f , the tile 1 has a positioning offset 33 formed along the periphery thereof and the rim projection 35 extends from and along the periphery of each of the panels 2 so as to index in the positioning offset 33 formed along the periphery of the tile 1 . in the embodiments shown in fig7 a - 7f , the above noted magnetic or pressure sensitive perimeter 8 can also be utilized if desired . fig8 illustrates an exploded cross - sectional view which is similar to that of fig4 but which shows an alternative embodiment of tile projection 4 . in this embodiment , a projection 34 is provided so as to extend from the top surface portion 3 of each floor panel 2 while the tile 1 has at least one positioning recess 36 formed therein such that projection 34 indexes into or with positioning hole or recess 36 formed in the tile . otherwise , this embodiment is similar structurally and functionally to the embodiment shown in fig1 - 4 . lastly considering then the embodiment shown in fig9 a and 9b , in this embodiment at least one peripheral recessed portion 40 is formed in each panel 2 while at least one corresponding peripheral projection 38 extends from the tile 1 . accordingly , the peripheral projection 38 is oriented so as to index in recessed portion 40 of each panel to again allow for orientation of the tile 1 to each of the panels 2 such that the tile is removable and replaceable without the use of indexing tools or fixtures and such that the tile is substantially of the panel module size . again , the modularity of panels is dimensionally consistent such that the tile 1 can be relocated on any of the panels 2 so as to maintain a consistent modular interface . furthermore , the use of a magnetic or pressure sensitive adhesive perimeter 8 ( not shown in fig9 a and 9b ) can also be utilized in this embodiment . obviously , numerous modifications and variations of the present invention are possible in light of the above teachings . it is therefore to be understood that within the scope of the appended claims , the invention may be practiced otherwise than as specifically described herein .