Thickness reduction arising due to corrosion or in any other way can cause severe damages to structures. Hence regular inspection of structures is vital in many industries. One of the factors deciding the replacement of a structure is the minimum thickness remaining in the structure. We introduce a novel ultrasonic method that precisely evaluates the minimum remnant thickness of structures. This method utilizes the cut-off property of SH1 guided wave mode. The numerical and experimental investigation of remnant thickness evaluation is discussed in this presentation.