A vertical blind assembly module includes a head rail unit with opposite sides and a unit axis extending between the sides, a housing and an axle pivotally connecting the housing to the head rail unit so that the housing can pivot about a pivot axis that is perpendicular to the unit axis. A slat is coiled in the housing so enabling the slat to be extended from the housing a selected distance and retracted into the housing. A foot rail unit is pivotally connected to the projecting end of the slat, the pivotal connection being collinear to the pivot axis. By turning the axle relative to the head rail unit about the pivot axis when the slat is extended, the slat can be turned between a closed position wherein the slat is parallel to the unit axis and an open position wherein the slat is perpendicular to the unit axis.