Acugauge® backflow testcock adapters are used by certified backflow testers when testing backflow preventer assemblies. To install, just apply a little teflon tape onto the male threads, then screw the backflow test cock adapters onto the the backflow preventer assembly you're testing. You would then couple the hoses from your backflow gauge onto the backflow test cock adapters and proceed with testing the backflow assembly. Tip: to prevent buying more adapters in the future, remember to remove adapters when you're finished testing the backflow assembly.