I'm trying to layout a 1x1 inch grid on a rather large map. I have had success using the define pattern technique before on smaller maps, but for some reason when I add the new fill layer for this pattern the 1x1 squares turn into a sort of plaid with rectangles and different size squares. I'm sure this is a ridiculously simple fix, but my efforts to search the interwebs have failed me.

Thanks in advance.