The check mark pattern is defined by higher highs followed by lower lows followed by even higher highs.  This pattern is most commonly seen as a continuation pattern.  The inverted check mark is the same pattern, but upside down.

These patterns are based on daily highs and lows.  The exchanges report highs and lows almost exclusively during market hours, so these alerts rarely if ever occur after market.  We never report these alerts before the open or in the first three minutes after the open.  The last part of the check mark must happen at least three minutes after the open.