A blind with a drive mechanism, wherein the blind includes at least one portion of sheet material which forms the blind, wherein the drive mechanism is configured to allow the height of the free end of the blind to be located at a predetermined position with respect to a window with which the blind is to be fitted, wherein the blind further includes an engagement system which, when engaged, acts to prevent rotation of the drive mechanism and hence retain the blind at at least one predetermined position intermediate the fully extended and retracted positions of the blind, wherein the drive mechanism comprises an elongate drive member which is operated by a user to adjust the position of the blind, wherein the engagement system includes an engaging member (34; 80; 94; 112) which is suitable to engage a portion of the elongate drive member, wherein the elongate drive member includes a formation portion at at least one location therealong, said formation portion being configured to engage with the engaging member to define the said predetermined position of the blind, wherein the elongate drive member is in the form of a cord which comprises a series of protruding portions spaced apart by a set distance; characterized in that the formation portion is provided as a length of said cord at which the spacing between the protruding portions is at a greater distance than the said set distance, wherein, when the formation portion is at the location of the engaging member (34; 80; 94; 112), retention means (38,50; 84,86;98;116,118) provided on the engaging member engage the formation portion and retain the elongate drive member and hence the blind at said predetermined position. wherein the blind includes at least one portion of sheet material which forms the blind, wherein the drive mechanism is configured to allow the height of the free end of the blind to be located at a predetermined position with respect to a window with which the blind is to be fitted, wherein the blind further includes an engagement system which, when engaged, acts to prevent rotation of the drive mechanism and hence retain the blind at at least one predetermined position intermediate the fully extended and retracted positions of the blind, wherein the drive mechanism comprises an elongate drive member which is operated by a user to adjust the position of the blind, wherein the engagement system includes an engaging member (34; 80; 94; 112) which is suitable to engage a portion of the elongate drive member, wherein the elongate drive member includes a formation portion at at least one location therealong, said formation portion being configured to engage with the engaging member to define the said predetermined position of the blind, wherein the elongate drive member is in the form of a cord which comprises a series of protruding portions spaced apart by a set distance; characterized in that the formation portion is provided as a length of said cord at which the spacing between the protruding portions is at a greater distance than the said set distance, wherein, when the formation portion is at the location of the engaging member (34; 80; 94; 112), retention means (38,50; 84,86;98;116,118) provided on the engaging member engage the formation portion and retain the elongate drive member and hence the blind at said predetermined position.