A trend does not usually die in one candle. It dies the way most things die: gradually, then all at once, with warning signs visible for anyone actually looking. The head and shoulders pattern is the clearest visual record of that gradual death that exists in chart reading: three rallies in a row, each one telling you a little more clearly that the buyers pushing the trend are running out of ammunition.
Reading it as a picture, three bumps that vaguely resemble a shoulder, a head and a shoulder, misses the point entirely. Reading it as failing structure, three attempts at a high with progressively weaker conviction, is what actually makes the pattern useful.
Anatomy of the three peaks
The left shoulder is a normal rally within an established uptrend, nothing unusual about it. The head is a higher high, often on strong momentum, that still looks like trend continuation while it forms. The right shoulder is where the pattern reveals itself: a rally that fails to reach the head's high, often stalling near or slightly below the left shoulder's level, on visibly less strength than the first two attempts. The weakening does not need to be dramatic. It needs to be real: fewer follow-through candles, smaller ranges, a slower approach to the failed high.
Shoulder symmetry and why it matters
The two shoulders do not need to be identical, but they should be roughly comparable in height and take roughly comparable time to form. A right shoulder that forms in a third of the time the left shoulder took, or one that sits dramatically lower, suggests the structure is not really a head and shoulders at all, just a downtrend with a bump in it. Symmetry is a rough filter for whether the pattern is genuine or forced onto a chart that does not really show it.
The neckline and volume clues
The neckline connects the low between the left shoulder and the head to the low between the head and the right shoulder, and it is frequently sloped rather than flat, which is normal and not disqualifying. The break of that neckline is the confirmation, the same logic as a double top's neckline break: the one level holding the pattern's structure together gives way. Volume, where it is visible and reliable, often tells the same story a second way: heaviest on the rally into the head, noticeably lighter on the right shoulder's failed attempt, and picking up again on the neckline break itself as trapped longs exit.
A worked example
Nasdaq forms a left shoulder at 19,240, rallies to a head at 19,340, pulls back to 19,180, then rallies again to only 19,290 on the right shoulder before rolling over, clearly short of the head and roughly in line with the left shoulder. The neckline runs from the low near 19,190, between shoulder and head, to the low near 19,180, between head and shoulder, essentially flat around 19,185. Price closes below 19,185 at 19,160. Entry on that close, stop above the right shoulder's high at 19,290, a 130 point risk, or a tighter stop above the most recent minor swing at 19,220 for 60 points. Pattern height from the head at 19,340 to the neckline at 19,185 is 155 points, projecting a target near 19,030. On a $10,000 account at one percent risk with the 60 point stop, that is roughly 1 to 2 contracts depending on the exact per point value used.