The chart shows many Flag patterns:

Flag Buy Signal
When price has moved higher and prices have consolidated, creating a channel of support and resistance, a buy signal is given when prices penetrate and close above the upward resistance line.
Flag Sell Signal
Assuming prices previously moved downward, then after a period of price consolidation, a sell signal is given when price penetrates and closes below the support line.
For more information on the concept of support and resistance, (see: Support & Resistance). Another similar pattern discussed is Triangles (see: Triangles).