[ITZREAL]

I was just flying a flight, and at the tail end of the flight, I was given a vector to Visual 21 approach. I looked at the procedure options available and saw that there was an option for a VOR 21 approach. I chose this option as it would give me a better option for a controlled vector approach. Once I had chosen this option, I was given a choice of VOR or HDH approach. I have flown many times using a VOR visual approach. I have never heard of an HDH approach. What is it? I chose the VOR 21 approach and landed just fine. But, what is the HDH approach? What does HDH stand for?