Gemrm is right--if you sew the borders together first then put on the quilt without mitering them you will end up with the inner border going across the outer border at each corner. You could do it with them joined if you miter them. If this doesn't make sense, take 2 markers of different colors and draw your quilt on paper and then put the two markers in your hand together and draw the borders like you'd normally sew on a border (for me that is sides first and then top/bottom)