Abstract: A universal tensioning device for blinds and shades comprises a U-shaped channel member which has oppositely disposed open ends which provide first and second access passages and a third access passage opening through the bottom wall of the channel member. A winding shaft is mounted for rotation in the side walls of the channel member and extends transversely across the channel directly above the third access passage. A ratchet wheel is provided at one end of the winding shaft and is located externally of a side wall of the channel. A socket is formed in the end of the winding shaft. A dog is pivotally mounted on the side wall of the channel member for movement into and out of engagement with the ratchet wheel. A biasing spring is provided for releaseably urging the dog toward the ratchet wheel. A pair of these tensioning devices are located in a chamber formed in the header rail of a venetian blind which also accommodates the slat angling mechanism and height adjustment mechanism.