The impulse's high= the retest of previous higher low, or previous NSH .
Retest = the wick of the candle at least touches the last NSH's close, or the last lower high's close but the candle doesn't close above these highs.
Note, price moves in trends. Price will stay in the trend until it shows the signs of reversal.
Sign or the trend reversal = violation of the last Higher Low or the last Lower High. Until then trend remains active.
See, notes on the chart.
I picked up the to enter long. Gartley's overall succes rate is about 60%. But when you combine it with the type of strucuter analisys I use - then It's rate rises to 75-78%
Have a nice day.