We study sign-restricted matrices (SRMs), a class of rectangular ( 0 , ± 1 ) -matrices generalizing the alternating sign (ASMs). In an SRM each partial column sum, starting from row 1, equals or and is nonnegative. determine maximum number nonzeros in SRMs characterize possible sum vectors. Moreover, results on interchange operations are shown, both for and, more generally, -matrices. The Bruha...