Petroleum refining company Sunoco ( SUN) is another commodity-driven name that's nearing an important technical level right now. In this case, the setup to watch is an ascending triangle that's been developing since shares of Sunoco bottomed back on Aug. 8. Traders should be watching for a breakout above sub-$40 resistance right now. While an ascending triangle is normally thought of as a continuation pattern, this setup has been a common reversal pattern lately. It's marked by a staunch, horizontal resistance level acting as a sort of "price ceiling" for shares and uptrending support below. As shares bounce between those two price levels, they get squeezed closer and closer to a breakout above resistance. The buy signal comes when shares breakout above their resistance level -- until that happens, this isn't a high-probability trade. We need to see the glut of supply of Sunoco at $40 get absorbed by buyers before it makes sense to take a position in this stock.