As the saying goes, there are many possible reasons for an insider to sell a stock, but only one reason to buy -- they expect to make money. So let's look at two noteworthy recent insider buys.

At RAPT Therapeutics, a filing with the SEC revealed that on Wednesday, Director Wendye Robbins bought 2,600 shares of RAPT, for a cost of $26.01 each, for a total investment of $67,632. So far Robbins is in the green, up about 14.7% on their purchase based on today's trading high of $29.83. RAPT Therapeutics is trading up about 5% on the day Thursday. Before this latest buy, Robbins made one other purchase in the past twelve months, buying $19,200 shares for a cost of $12.00 each.

And at Ampco-Pittsburgh, there was insider buying on Monday, by Director Carl H. Pforzheimer II who purchased 20,000 shares at a cost of $2.85 each, for a trade totaling $57,020. Ampco-Pittsburgh is trading up about 4.1% on the day Thursday.