Sealing techniques have been perfected which utilize the properties of fluorocarbon plastics to make high vacuum seals. Several designs are described in which confined gaskets are used instead of O‐rings, with consequent reduction of contamination from outgassing and permeation. These sealing techniques have been incorporated into a series of modular components which may be used for assembly of high vacuum systems. Some of these components are movable joints which allow leak‐free motion between parts of a system. While not suited for high temperature bakeout, systems constructed from these modular components are capable of being pumped below 10−7Torr. Dependable systems can easily be assembled or modified using these components, with no detectable helium leaks at a level of 2×10−10std cm3/sec.