the front bottom plate segment 48 is forward of the mid bottom plate segment 46 which is forward of the rear bottom plate segment 44 the front bottom plate segment 48 is attached to a bottom front portion of the forward side edge plate 40 approximately perpendicular to the second forward edge plate 40 as best seen e g in fig2 and 4 the rear bottom plate segment 44 mid bottom plate segment 46 and front bottom plate segment 48 do not necessarily lie on a plane and rather are angled relative to each other in other implementations the bottom plate 43 may be formed as a single e g bent plate having angled portions referring e g to fig2 the mid bottom plate segment 46 and front bottom plate segment 48 each has a plate leading edge 50 52 that together form a discontinuous front leading edge 54 for cutting engagement with the substrate s the front leading edge plate 54 is angled laterally by angle b of fig3 e g about 10 u00b0 to about 35 u00b0 the angled front leading edge plate 54 may or may not have teeth mounted thereto however in the implementation shown in the.