A break of structure, or BOS, happens when price breaks the most recent swing point in the direction of the existing trend. In an uptrend, a BOS is a break above the last swing high; in a downtrend, it is a break below the last swing low. A BOS confirms continuation.
Why it matters
A BOS is the market confirming that the current side is still in charge. When an uptrend prints a new higher high above the previous one, it has completed another HH/HL cycle — an objective sign that buyers are still winning. It turns a hopeful bias into a confirmed one.
How to use it
Many traders wait for a BOS and then look for an entry on the following pullback, rather than chasing the break itself. A useful filter is to require a candle close beyond the swing point rather than just a wick, which helps filter out weak, temporary pokes through the level.
A break of structure confirms the trend continues — it breaks the last swing in the trend's own direction.