Hi SG
I think as Murthy mentioned if it's warning lines you're referring to , let me explain when they are used.
The Median line method has the concept that price will move forward on a path with a mathematical relationship based on the earlier swing move and the median line set will provide the support and resistance levels. When 3 significant points where price has changed direction are chosen and a median line drawn from point A through 50 % of line joining point B and Point C, the probabilities of the price move from Point C has been described with 4 rules ...see post
http://www.traderji.com/advanced-trading-strategies/59403-trading-median-lines-andrews-pitchfork-5.html#post607742
From what I have learnt on reading and applying this concept ,this method identifies support / resistance zones where high probable reversal / breakout can occur and combining with additional confirmation like stochastics or any other momentum indicator, daily pivot levels we can project entry and exit levels.
Coming to warning lines, the lines are drawn when the price moves out of the Current Pitchfork, either on the upside or downside.When this happens , parallel lines are drawn at a distance equal to the 50 % range of the current pitchfork.These lines have the same properties as upper median line parallel / lower median line parallel ie they will also act as resistance / support levels when price meets them.It is similar to range expansion.
In fact today's nifty chart, the warning lines have been drawn to estimate the price move expansion from the initial PF drawn.Adding a link to the post.
http://www.traderji.com/futures/53485-nifty-entry-exit-target-levels-median-line-charts-22.html#post616800