The 4-point probe method is a non-destructive method for measuring the resistivity of a sample. In the case of a thin metal layer, this allows its thickness to be measured. Tokamaks face erosion problems and require a non-destructive characterization method that allows micrometric precision. A collaboration between the IRFM and LAPLACE has made it possible to apply this method to the characterization of components exposed to plasma. The 4-point probe method is already widely used in microelectronics to calculate the electrical resistivity of semiconductors, but other applications are also possible in other fields, such as aerospace and nuclear power, in which erosion issues are also concern.