This duplex coupling is used to join two beer lines together, via hex nut, when cleaning your double tap system. This is convenient for people that do not want clean the lines separately.
To use this connector, remove each coupler and connect the hex nuts together with the duplex coupling. Run your cleaning solution into one of the faucets on the tower. Place a bucket below the other faucet and open it to let the solution flush out into the bucket. This coupling will save you from doing the same cleaning process twice.