The RNA Morphology is demonstrated in this figure by the letters H (Hairpin Loop), I (Internal Loop), B (Bulge), and M (Multi Branched Loop). These symbols can be used to describe the morphology of a structure in the form of a tree list.
The structure can also be encoded as the region table in the lower right corner of the figure. The left most number is the location of the 5' start position of the stem. The second number is the location of the 3' ending position of the stem, which is paired with the 5' starting positions base. The last number is the number of paired bases in the stem. In some cases the region table will contain a fourth column which contains the energies, although this is not necessary to construct the secondary structure.