Example
Head at 105.5, neckline at 101.8: height 3.7, target 101.8 − 3.7 = 98.1.
In practice
A measured move gives a first target when there is no obvious level ahead. The logic is that the forces that built a pattern tend to produce a move of similar size once it resolves.
It is also a quick test of whether a trade is worth taking: if the projected target is only a little further than the stop distance, the reward does not justify the risk.
What to watch for
It is a rule of thumb. Levels standing between the entry and the projection matter more, and price owes the projection nothing.