The horizontal hash mark indicates where a stock closed. At the bottom of an Investor's Business Daily chart you can find a stock's trading volume. Volume is a key part of a stock's action. Look at both daily and weekly charts. Daily charts give you a close-up view, and are especially helpful in spotting buy and sell points.
Charts help put a stock's action in context.
Likewise, a big point decline may look ugly on a chart, or just be a normal pullback in light volume. Many investors dismiss charts as meaningless. Just buy shares of great companies, they say, and don't bother trying to read the market equivalent of tea leaves. Investors should look for companies with superior fundamentals. Insist on strong earnings and sales growth, and superior profit margins and return on equity.