You don't have to be an expert technical analyst to figure out what's going on in shares of mining and petroleum giant BHP Billiton ( BHP) -- the setup in the $112 billion stock is about as basic as it gets. BHP has been bouncing higher in an uptrend since July, hitting a floor on a trendline support level all the way up to today's close. >>5 Stocks Insiders Love Right Now The channel in BHP is important because it provides us with a high-probability range for shares to stay within both on the upside and the downside. More important, trendline support has halted shares' pullbacks perfectly on the last four touches of the level - now we're hitting touch number-five. A bounce in today's session is the buy signal in BHP. Buying off a support bounce makes sense for two big reasons: It's the spot where shares have the furthest to move up before they hit resistance, and it's the spot where the risk is the least (because shares have the least room to move lower before you know you're wrong). Remember, all trend lines do eventually break, but by actually waiting for the bounce to happen first, we're ensuring the BHP Billiton can actually still catch a bid along that line. Keep a tight stop in place under the channel if you decide to buy here.