High tight flag chart pattern forms when a stock rises over 90% (preferably 100%) or more in two months, then consolidates sideways for 15-25 days with a decline of no more than 25%. When there's a breakout of the sideways 'flag' on high volume , the powerful uptrend often resumes.
The entry point is either as the stock breaks the high of the flag or breaks a downtrend line - but only ever on higher than average volume/
With a decline in the flag of 15%, would be looking to enter on a breakout of the high of the flag with higher than average volume.