A CD ladder can be a good investment strategy when you have a nice sum of money available (say, $500 to a few thousand or more) and can afford to lock up your money for a period of time, from six months to several years. It is best used when rates are relatively high, especially since you can shop around for the best rate at each “rung” on your ladder. This type of investment strategy is best suited to those with a relatively low risk tolerance and who will be satisfied with a modest but steady interest rate.