Support, Resistance and Breakouts

Three mechanisms, and all three are about real orders rather than about the number itself. A price level has no properties; the people transacting around it do.

1. 1Resting ordersParticipants place limit ordersLimit orderAn instruction to trade only at a stated price or better, guaranteeing a price but not a fill.Read the full explanation at round numbers and at previous extremes, and those orders are real supply and demand sitting in the order bookOrder bookThe live list of resting buy and sell limit orders at each price for a security.Read the full explanation.
2. 2MemorySomebody who bought at a level and watched it fall often sells at break-even when it returns. Somebody who missed the move buys the retest.
3. 3Volume historyA price where a great deal of stock changed hands has many holders with a position and a decision to make when it returns.

The third is the most durable and the least discussed. A level where enormous volume traded is a level where a large population of holders has a cost basis, and cost basis is the single most reliable predictor of when somebody will act.

Drawing a level at exactly 47.83 implies a precision that does not exist. Support is a region, typically wide enough to accommodate a percent or so of noise, and treating it as a line produces a stream of technically-broken levels that then hold anyway.

A practical convention is to draw the zone from the body extremes to the wick extremes of the bars that formed it. That gives a band rather than a line, and it is honest about the fact that the level was never one price.

When resistance breaks it commonly becomes support. The participants who sold at that ceiling repeatedly have been proven wrong; those who bought the break want to add on a pullback. The order flow at the level flips sides, and the level keeps mattering with its role reversed.

This is one of the more reliable observations in the field, because the mechanism is legible. It is not that the number acquired a new property; it is that the population of holders around it changed sides.

The same logic explains why the third or fourth touch of a level is more likely to break than the first. The seller who was defending it has been filling orders each time, and eventually they are finished.

Price moving through a level and immediately returning is common enough to have its own vocabulary. The move traps participants who acted on the break, and their exits push price back the other way.

This is why a failed break sometimes leads to a sharp move in the opposite direction. It is not a mystical reversal; it is a population of positions being closed at once, on top of the stop ordersStop orderA resting instruction that becomes a live order only once price trades through a trigger level.Read the full explanation that were resting beyond the level.

Not every level comes from prior trading. Some prices attract attention because of what they are rather than because of what happened at them, and orders cluster there for that reason alone.

• Round numbers: whole dollars, then tens, then hundreds. Limit and stop orders cluster at them measurably.
• The prior close, the open, and the previous day's high and low, all of which are published everywhere.
• An IPO price, which is where an identifiable population of holders acquired their shares.
• A prior gap, whose edges are visible and frequently referenced.
• A 52-week high or low, which appears on screens and in scans across the entire market.

The last of these is the most consequential because it is a screening criterion rather than a chart observation. A security making a new 52-week high appears in lists that many participants look at, which brings attention that had nothing to do with the chart.