A pennant more than 12 weeks old would turn into a symmetrical triangle. The reliability of patterns that fall between 8 and 12 weeks is debatable. For a bullish flag or pennant, a break above resistance signals that the previous advance has resumed. For a bearish flag or pennant, a break below support signals that the previous decline has resumed. Volume should be heavy during the advance or decline that forms the flagpole.
Heavy volume provides legitimacy for the sudden and sharp move that creates the flagpole.
Even though flags and pennants are common formations, identification guidelines should not be taken lightly. It is important that flags and pennants are preceded by a sharp advance or decline. Without a sharp move, the reliability of the formation becomes questionable and trading could carry added risk. Look for volume confirmation on the initial move, consolidation and resumption to augment the robustness of pattern identification. HWP provides an example of a flag that forms after a sharp and sudden advance.