Find the all time high (ATH) and plot a horizontal line extended from the ATH out to the right. Script also produces a label near the current candle indicating location and value of the ATH. If the ATH is higher than the current candle's high the label will be red and pointing up to indicate the ATH is above the current candle. If that current candle's high is the ATH, the label is green and pointing at the current candle's high.