Should an investor take profits in a stock if heavy volume accompanies a sharp break of the 50-day or 10-week moving average? Yes! If a stock falls below its 50-day line in heavy trade and can’t seem to bounce back, buying demand may be drying up fast. That could mark the end of a stock’s run. These lines act as a price support level for market leaders during an uptrend, but can also serve as resistance in a downtrend.