The novel extension of the synthetic aperture radar (SAR) technique to the terahertz (THz) spectrum has emerging short-range applications, especially in an indoor environment. One of the potential applications is a wall scanner, which can assist in precisely locating and classifying objects in a wall such as electrical wires, components of metal, wood, and plastic. Additionally, the wall's structural integrity and failure can be extracted. Considering such application in the foreground, this paper addresses through-wall sensing at the THz spectrum employing the SAR technique. In this work, a small version of a wall using gypsum plasterboards is constructed. This model also consists of electrical wires and components made of metal and wood mounted between the plasterboards. It is quite similar to indoor wall construction in a practical environment. Further, a vector network analyzer (VNA) based testbed is employed and measurements are recorded in both transmission and reflection modes for three frequency spectrums, which are 75-110GHz, 220-330GHz, and 325-500GHz. The transmission measurements present the sensing capabilities behind the wall and provide relative attenuation among different frequency spectrums. In reflection mode, a 2D planar SAR trajectory is implemented to reconstruct a 3D image of the wall. The image is analyzed for identification and precise localization of the wires and other components within the wall.