A blind flange is a solid disk used to block off a pipeline or to create a stop. Similar to a regular flange, a blind flange has mounting holes around the perimeter and the gasket sealing rings are machined into the mating surface. The difference is that a blind flange has no opening for fluids to pass through. Instead, it is placed in between two open flanges, which stops the flow through a pipe. Many times this type of blockade is used when adding another line onto an existing pipeline or when a new valve is being added.