Adjustable Trailing Arm Mounts?

[chevychase]

I was thinking about some of my parts I have stored away. I got two brackets that I was told were adjustable trailing arm mounts. I don't have a pic, but here is an illustration of the side view. I guess you have 3 positions to raise/lower the trailing arm. What would be the benefits and has anybody ever heard of such a thing or have I been bamboozled?