An overhead projector for transparencies is provided, and includes a conventional top glass or other transparent plate. The overhead projector also includes a conventional optical system including a projection light path. An additional glass or the like plate is supported above the top conventional glass plate and supports a transparency for projection. A masking member is provided either above or below the transparency. The masking member is movable to cover portions of the transparency while uncovering other portions thereof to project selected portions of the transparency at any given time. In addition an arrow or other message carrying unit is provided which may be above or below the transparency, and which is movable to direct attention to a particular area of the transparency.