UK OHJs
An OHJ is what it says on the tin, an overhead join; it doesn't matter whether you join from N,E,W or S. Others in this discussion have related their experiences at joining in all kinds of other situations but what they are describing is something different. Others have pointed out possible dangers in doing OHJ but this not answering the question.
Please take a look at Pooleys entry for Shoreham: they require you to carry out an OHJ so it's just as well to understand this procedure.