Make sure you have the right amounts in the right accounts because smart moves today can boost your wealth tomorrow. With a bond ladder, you’re staggering your investments so that you have different bonds coming due at different times. With stocks, you’re not locking in to a specific time frame — you can buy a stock one day and sell it two weeks later if you see fit. It’s presented not as a mathematical model for you to use, but as an example of the kinds of considerations that affect the value of a bond you might buy or sell at a discount.