The reading direction of a structured ncRNA can be identified by evaluating the differences of the above descriptors between both strands. To be precise, the difference Δx of descriptor x is defined as Δx = x+ - x-, where x+ denotes the value of x in reading direction of the input alignment and x- the value of x in the reverse complementary alignment. Hence, Δmeanmfe and Δmeanz capture the energetic differences between both strands, while Δconsmfe and Δsci describe the differences in structure conservation.