Abstract: A collaboration tool is presented for accurately guiding two or more communicating users to reference common locations in similar but separate architectural drawings. The collaboration tool includes a transparent planar sheet having at least one squared corner, and a grid of squares imposed on at least one side of the transparent sheet. The grid of squares has an X axis and a Y axis originating from the at least one square corner. Each square in the grid of squares is associated with a unique X-axis designator and a unique Y-axis designator. The apparatus further includes an aperture provided within each square of the grid of squares, for allowing a marking instrument therethrough for making a mark at a designated location on an architectural drawing underneath the transparent planar sheet.