 The subdivision complex can be created by gluing together the opposite edges of the square , making the subdivision complex <formula> into a torus . The subdivision map <formula> is the doubling map on the torus , wrapping the meridian around itself twice and the longitude around itself twice . This is a four @-@ fold covering map . The plane , tiled by squares , is a subdivision complex for this subdivision rule , with the structure map <formula> given by the standard covering map . Under subdivision , each square in the plane gets subdivided into squares of one @-@ fourth the size . 
