I did it a little differently. I made the two grids on different layers to use a guide in GIMP. Then when I went to save I turned off visibility of these layers. Thanks for the help as it works great for my needs. Although, I figured out I don't need to draw the walls using the rectangle select and then fill. I now just draw lines with the line tool using a 20px wide brush. This works well as I can snap to the grid line but the "wall" bleeds over the grid line which allows the players to see the "wall" after I lay down my VBL.