This is always sold with the camera; it consists of a wooden frame, with two shutters, the one opens on hinges, and allows the plate, which has just been removed from the nitrate of silver bath, to be inserted, with its collodionised face placed towards the sliding shatter, which must be kept closed. The frame is provided at the corners with pieces of wire, which prevent the plate from coming in contact with the sliding shutter. Close and fasten the hinged shutter, and the frame is then ready for use. Remove the ground-glass screen, place the glass frame in its place, with the collodion side towards the object, then on raising the sliding shutter the time must be noted in seconds for the desired exposure. Close the sliding shutter, remove the frame to the dark room, and take out the plate by opening the hinged shutter.