Many optical components in the visible or near infrared make use of thin film evaporation technology to produce coatings for narrowband filters, high-frequency and low-frequency pass filters, beamsplitter and antireflector coatings. The extension of these techniques to wavelengths beyond 50 um is virtually impossible due to absorption and the difficulty of adhesion of thick films. Many devices however can be fabricated using metallic mesh or its complementary structure as the reflecting elements in interference filters. This paper will discuss the performance of such filters, of either bandpass or blocking characteristics, and the application of these structures to high-resolution spectroscopy. Beamsplitters using the polarization properties of metallic mesh will also be discussed.