Short Term Trading Weekend lounge 9th-11th Dec, page-32

Gap theory must be one of dumbest TA indicators i have ever seen but the majority of traders use them and as such most of the time its a self fulfilling prophecy.

As an example NAE today. 2nd highest volume day of the year and it gapped up on open but closed near the days highs. So tens of millions of shares traded higher than the gap and lower than the closing price. Bet ya there are many many traders sitting on the sideline waiting for the gap to fill.