Abstract: A transparency block is disclosed which is attractive in appearance and provides a maximum of image area for any given dimension of block. An important feature of the invention is the use of locking fingers of unique construction for holding transparencies firmly in the block, and without the need for tape or mechanical mounting. Another feature is the provision of a built-in circline fluorescent lamp for providing maximum illumination of the transparency at a minimum of energy expenditure or cost. The block may be hung horizontally or vertically, and is so designed that it may be used in isolated manner or grouped with other or similar blocks, as may be required. For this purpose, it has a built-in recessed outlet for uncluttered interconnection with other similar blocks.