The Triggerline Indicator is a useful and popular free Forex indicator for the MT4 trading platform. It is used to identify the trend direction and strength of a currency pair. The Triggerline Indicator is based on the moving average of price action and uses a signal line to help traders identify when the trend is changing. The Triggerline Indicator is easy to use and is a great tool for traders looking to identify the trend and momentum of a currency pair.