The default is Scrolls => false. If the option Scrolls=>true is given, then a triple is returned, with the ideal first followed by xmat and ymat, the smaller and larger of the scrolls containing the carpet.
Functions with optional argument named Scrolls :
canonicalCarpet(...,Scrolls=>...) -- see canonicalCarpet -- Carpet of given genus and Clifford index
carpet(...,Scrolls=>...) -- see carpet -- Ideal of the unique Gorenstein double structure on a 2-dimensional scroll