[en] Backscattering of gamma-rays has for a long time been used for measuring density, concentration, and thickness. The input of these gauges is usually composed of a mixture of single and multiple back-scattered gamma-rays. In the present experiment, these two components were measured separately by changing collimators of different size which were placed in front of a detector. In the case of low atomic number scatters, the multiple backscatter component increases to considerable extent. Comparison of thickness measurements by detecting the multiple backscatter component only and single backscatter one only showed that the former was, for instance, 1.4 times as long as the latter in the maximum measurable range with a carbon brick wall. The conventional thickness measurement using total backscatter is almost the same as for single backscatter in the maximum measurable range