displaces in the wide portion of the tapered slot 60 while the lower portion of support track 16 pivots about pivot area p in the narrow lower portion of support track 16 of slot 60 when reconfigured to the fully tilted configuration as shown in fig5 the formerly vertical walls of support track 16 become substantially parallel to the angled second inner wall 72 such that walls of support track 16 form angle u03b8 with respect to the vertical inner wall 70 of slot 60 meanwhile gap g fig4 substantially closes as the longitudinal axis of flange bolt 52 tilts along with support track 16 thus the axial end of support track 16 is tilted within slot 60 such that the outer surface of track 16 faces upwardly as shown in fig5 this upward tilt also tilts the rest of the longitudinal extent of track 16 including its center portion if the center portion had a central dip or low point as noted above this upward tilting may render the center portion substantially level moreover the amount of tilt imparted to support track 16 may be finally adjusted by rotating flange bolt 52 to achieve any desired tilt within the tilt range allowed by the taper of slot 60 in an exemplary embodiment the maximum tilt angle u03b8 is about 2 degrees though it is appreciated that other tilt angle ranges may be provided as required or desired for a particular application in some applications the maximum available tilt angle u03b8 may be varied by increasing or decreasing the amount of taper within slot 60 and may be set as low as 0 5 degrees 1 degree or 1 5 degrees and may be as large as 2 5 degrees 3 degrees or 3 5 degrees or.