The diffracted field due to an E-polarized plane wave incident on two cylindrical wedges forming a slit-type aperture is formulated using an integral equation for the surface current. The use of the ordinary method of moments to solve for the unknown surface currents does not yield a convergent solution, owing to the semi-infinite dimensions of the wedges and the fact that the total current does not vanish on the illuminated surface for this type of excitation. Therefore, the surface current is divided into two components, namely, a known noninteraction term and an unknown term due to the infinite number of interactions between the wedges. The noninteraction term is considered to be the physical optics current for those geometries that have wedges with nonsharp edges, whereas the exact surface current for a single wedge is used for double wedges with sharp edges. The interaction term may be evaluated using the ordinary method of moments, because it decays with increasing distance from the edge along the surface of either wedge. It is found that this technique leads to an efficient solution and makes it possible to use the method of moments for the multiple scattering by bodies of semi-infinite or large dimensions. Numerical results for the diffracted fields and transmission coefficients for a variety of related structures, such as the thin slit, the thick slit, the double truncated wedge, and the double capped wedge, are presented and compared with available solutions.