I'm new at this but, I've also done plenty of research and looked at a bunch of charts. I could be wrong for sure, check out these links (copied text so you dont have to go to the site if not interested)
~ For confirmation, traders will commonly look for a downward sloping neckline before entering a trade on the break of a head and shoulders pattern and an upward sloping neckline before entering a trade on the reverse head and shoulders, as this is further indication that the trend is reversing. Secondly traders like to see the volume on the second peak (trough with a reverse head and shoulders) be lower than the volume on the first, and the volume on the third peak (trough in a reverse head and shoulders) be lower than the volume on the second peak as this is further confirmation that the trend is ready to reverse. Lastly, they will look for increasing volume on the break of the neckline to show that the break is real.
~ With inverted head and shoulders the neckline is drawn through the highest points of the two intervening peaks. A downward sloping neckline signals continuing weakness and is less reliable as a reversal signal.
The extent of the breakout move can be estimated by measuring from the top of the middle trough up to the neckline. This target is then projected upwards from the point of breakout.