Rebecca Walser, a wealth management advisor who specializes in financial planning for high net worth individuals, tells CNBC Make It that the rich use plenty of tricks to build wealth, but “the most common one is something that most regular Americans don’t even know a thing about: Investing in permanent life insurance policies.”

Permanent life insurance policies, which Walser discusses in detail in her book, “Wealth Unbroken: Growing Wealth Uninterrupted By Market Crashes, Taxes, And Even Death,” allow you to build savings in a tax-advantaged account.

Unlike term life insurance policies, which are cheaper, temporary and have pay-outs that are only accessible upon death, permanent policies offer a cash-value component.

Here’s how they work: You invest a lot of money into an account, basically “over-funding” it, and watch it grow, tax-free, says Walser. And that’s money you can access during your lifetime.