Double-loop networks have been widely studied as architecture for local area networks. The L-shape is an important tool for studying the distance properties of double-loop networks. Two L-shapes are equivalent if the numbers of nodes k steps away from the origin are the same for every k. Hwang and Xu first studied equivalent L-shapes through a geometric operation called a 3-rectangle transformation. Rödseth gave an algebraic operation, which was found by Huang, Hwang and Liu to correspond to the 3-rectangle transformation. Recently, Chen and Hwang obtained all equivalent transformations for the nondegenerate case. In this paper, we do the same for the degenerate case.