Good question. Technically, the top of the gap would be Friday’s close with the bottom of the gap today’s opening price. However, I like to look at the tops & bottoms of the surrounding candles & factor that in when factoring gaps into my analysis. On the 60-min QQQ chart that I’ve covered recently, I have a resistance level at 382.00. I added that as a support level before & since then, QQQ tested it a few times, then took it out with a big red candle, backtested with the next five 60-min candles, including Friday’s final candlestick. As such, that is probably as, if not more significant than the top of the gap (Friday’s close of 379.86 (just a hair below). Also, it isn’t unusual to see a slight move above the top of a gap (or below the bottom of one) before a reversal after it is backfilled, especially when there is strong momentum leading up to the backfill, as there was today.