A flag, or marker for identifying the locations of a plurality of tissue cassettes containing mounted Formalin Fixed Paraffin Embedded (FFPE) tissue specimens once removed from a tissue cassette/block storage system. The invention comprises a rectangular cuboid body member having front, rear, left, right, top, and bottom surfaces which substantially approximates the shape of a predefined number of tissue cassette/blocks, with a recessed area with grooves to accept one tissue index marker card for recording the patient's case information, or other relevant information. When multiples of the present invention are used within a tissue cassette/block storage system, they point to locations where pluralities of tissue cassette/blocks should be returned, and provides a support structure for neighboring tissue cassette/blocks within the storage location from becoming askew or damaged within the tissue cassette/block storage system.