Abstract: A check valve to be interposed between a source of pressure and a device to be moved by the application of the pressure. The valve has a passageway communicating with the source of pressure and a passageway communicating with the device. There is a valve seat formed between the two passageways and a valve member contacts the valve seat. A valve stem can move the valve member to rest on the valve seat to close the valve but the stem is separate from the valve. With lessening of pressure in the source of pressure beyond a desired level the check valve may be closed. Movement of the valve stem to a position away from the valve member ensures that the valve will open but only when the pressure on each side of the valve is about the same. A particular application is to protect the lip of a head box in a paper making machine but may applications are possible.