A spectacle blind consists of two metal discs connected by a steel plate, making it resemble a pair of glasses, according to the Steinmans, LLC website. One disc has an opening, while the other is solid.
Welding is not required to attach the blind to the pipe. The blind is typically attached as a permanent fixture and is effective for controlling flow in smaller pipes subject to higher pressure and temperature.
The blind typically fits between two pipe flanges and the gaskets. Installing, removing, and switching the line from open to closed usually requires an open area, making the blind unsuitable for use in narrower spaces.