Abstract: A slide body of a rigid transparent material is sized to be received within a slide transparency projector. The slide body includes a bubble level indicator having a narrow arcuate chamber which is filled with a liquid to create a bubble of air trapped within a band of fluid. The bubble is displaceable within the arcuate chamber and remains at the highest point therein. When the slide is level, the bubble rests at the mid-point of the band. The slide body is also provided with a pattern of concentric rectangles and a pattern of markings to indicate the extent of deviation of the bubble from its position at the mid-point of the band. The arcuate band, bubble and pattern of markings are projected onto the screen by a projector to permit a projectionist to readily ascertain whether or not the projector is in focus and is level. The projector can then be focused and leveled by adjusting the focusing and leveling system of the projector.