What is an Erling brick?
I definitely know them as the headlight brick, and they look like this:



HoMa's world of bricks has a nice page dedicated to this brick!

http://www.holgermatthes.de/bricks/en/lampenstein.php

LEGO's Pick a Brick lists this as an "Angular Brick 1x1", Design ID 4070 (equivalent to the piece/part id).