With a stock trading at $35, let's imagine that your theoretical pricing model shows 40 calls offered $0.75 below their theoretical value. Since each contract represents 100 shares, this adds up to a theoretically riskless profit of $75 per contract. To lock in this profit, you would buy the 40 calls (with a 38 delta) and sell 38 shares of stock for every 40 call you purchased. In this way, you establish a delta neutral position.