Calculated Industries 6020 is a digital plan measure that helps you take Linear, Area, and Volume measurements quickly and accurately. It features 72 built-in scales, including 39 Imperial and 33 Metric, making it suitable for various applications. You can also set six custom scales for faxed or out-of-scale plans. With two built-in memories, you can quickly solve for Area and Volume or accumulate and store two different measurements. It also has a lock switch to prevent accidental changes while rolling and a subtract measurement key to deduct distances rolled while pressed.