An interception would involve crossing the line of flight to initiate (usually Right to Left to take up station).
Here is the summary
http://www.caa.co.uk/docs/33/SRG_GAD_WEBSSL11.PDF
Pilots of Royal Air Force aircraft carrying out practice interceptions of smaller helicopters in the UK may care to note that the 'Helicopter will Rock' when the intercepting aircraft crosses the path of the interception small helicopter, thus giving the understood and will comply response automatically.
