Abstract: The signature of a closed manifold is an important invariant in geometric topology. Recently, Higson, Xie, and Schick proved an invariance theorem for the K-theoretic signature in codimension 2. However, the L-theoretic counterpart of this result remains an open problem. In this talk, I will describe how to achieve the L-theoretic counterpart of their result and provide some examples. I will also explain the basic ideas of the proof, highlighting the key steps and challenges involved.