Whenever a failure (momentum cut‐off) is imminent, the trigger line can be used to confirm the change of the trend. The trigger line is mainly used as a signal line for routine confirmation and for a conservative trade entry; in a word, it is the legitimate mark of the trend's failure. This chapter presents that the trigger lines behave in the same way, when touched or penetrated, as the median or their associated lines, especially when it concerns testing, piercing or zooming. The trigger line serves as a borderline for the whole market when it belongs to a contextual (major) pitchfork. The trigger line is an indispensable tool used for confirmation and entry decisions. A trend failure will convert a trigger line into a Hagopian line.