as shown at 150 accommodates the knife 110 to allow slidable mounting and fastening of the knife in each respective groove as shown in fig7 a shim 180 or shims of varying thicknesses may be utilized in the grooves under a blade to modify the heights of the blade in use the top 160 and bottom 170 members fit together in ridge in groove fashion similarly to the fit of the top 16 and bottom 17 members of the first embodiment shown most clearly in fig1 and 2 a wing nut and bolt not shown identical to wing nut 27 and bolt 24 are utilized to facilitate fastening the members together as in the first embodiment tightening the wing nut on the bolt eventually changes the knife mounting from slidable to fixed as desired by a user further to the explanation in the first paragraph of the detailed description in use the second embodiment 100 of the present invention has exactly the same function as the first embodiment 10 with the exception that the diagonally cut chamfer type sides 171 172 173 174 are larger creating an octagon shape tool 100 in any case the face of the tool out of which the blade 110 is extended is positioned flush against the side of the ceiling tile 12 fig1 with both being positioned on a flat surface the tool is drawn across the length or width of the ceiling tile depending upon which surface of the ceiling tile.