The aim of the present work is to find a pertinent parameter characterizing gaskets, such as used in joints in metallic enclosures, over the [100kHz - 100MHz] frequency band. The proposed test device provides a frequency measure of the coupling, between two wires placed on both sides of the assembly. We can then define an equivalent generator on the reception line. Then, starting from Latham’s analysis , we have obtained a pertinent parameter considered as a transfer impedance. This transfer impedance behaves, at low frequencies, like a surface impedance and thus can be taken into account in numerical codes, as, for example, codes based on the EFIE.We have modeled our experimental device and we have used the above technique to characterize an elastomer gasket in an overlap-type joint. The value of the coupling function is obtained numerically using a reciprocity technique because the direct calculation is not precise enough (signal of the order of magnitude of the numerical noise). We have compared the numerical results with those obtained from measurements, and we have obtained a good agreement between them. We will analyze the different physical mechanisms and discuss the domain of validity of this technique.