Abstract: A portable sun block releasably connectable onto a transparent non-porous panel such as a window of a vehicle. The device is particularly useful for being selectively positionable by a suction cup onto a vehicle window for blocking or reducing the intensity of sunlight or other vehicle's driving lights from entering into the vehicle and striking an occupant's eyes. With the inclusion of a unique suction release valve, a user may quickly and easily release the vacuum grip of the device against a window for repositioning and re-engagement or removal. By this arrangement, deployment against a window or the like is a simple one-step procedure whereby the valve is closed simultaneous with pressure against its control knob to re-adhere the device.