Americans like their 401(k)s, but can be pretty clueless about how to use them to maximum effect—leaving them less-than-well-prepared for retirement.

Findings from a survey from the Guardian Insurance & Annuity Co. Inc. included this and other unsettling news, such as how few Americans understand some of the basic terms needed to use a 401(k) efficiently and how few understand how to get the most from their plans.

The "Guardian Small Plan 401(k) RetireWell Study SM2.0: What's Working and Not Working for Small Plan Participants" revealed that, while 50 percent of respondents said they'd heard of target-date funds, 45 percent had heard of dollar cost averaging and 39 percent were familiar with target risk funds; while 66 percent of those claiming familiarity with target-date or target risk funds didn't really know what those terms meant. In addition, 77 percent say they've heard of vesting, but fewer than half understand what vesting is.