This little tap has been fastened to the sealed system on this Whirlpool french door refrigerator. This tells me that some technician in the past saw a need to add refrigerant, R134A according to the compressor, to this refrigerator.

Sometimes doing this can give a dying fridge a few more years life and keep it out of the landfill. But it’s technically illegal if not done according to EPA guidelines and leaving this temporary tap in place, instead of brazing it closed indicates this was not done correctly.