Abstract: A clutch mechanism (9a, 9b) for a vertical venetian blind is disclosed in which a first clutch part (9a) is mounted for sliding relationship on, but non-rotatable with respect to, a rotatable drive shaft (8). A second clutch part (9b) has a cylinderical portion (9e) surrounding the hub (9f) of the first clutch part (9a). The second clutch part (9b) is mounted for rotation about and slidably movable along the axis of drive shaft (8). Toothed gear faces (10a, 10b) on clutch parts (9a, 9b) are engageable upon rotation of the drive shaft (8) to rotate a hook (14) carrying a slat (1b) to rotate the slat. The walls (2a, 2b) of the housing (2) are resilient to permit axial engagement and disengagement of the gear faces (10a, 10b). When the slat (1b) has reached the limit of its travel, a worm (11) on part (9b) engages a stop (15or 16), preventing further rotation of part (9e).