A symmetrical triangle is composed of a series of two or more rallies and reactions in which each succeeding peak is lower than its predecessor, and the bottom from each succeeding reaction is higher than its predecessor. A triangle is therefore the opposite of a broadening formation since the trend lines joining peaks and troughs converge, unlike the orthodox) broadening formation in which they diverge.

These patterns are also known as coils, because the fluctuation in price and volume diminishes as the pattern is completed. Finally, both price and (usually) volume react sharply, as if a coil spring had been wound tighter and tighter and then snapped free as prices broke out of the triangle. Generally speaking, triangles seem to work best when the breakout occurs somewhere between one-half and three-fourths of the distance between the widest peak and rally and the apex. The volume rules used for other patterns are also appropriate for triangles.