MEASURE TWICE, LOOK ONCE

If you need to measure more than one side of an object (for example, if you're measuring a box, and you need both the height and width), you can measure both at the same time. First, open the Info palette (so you can see the measurements that the Measure tool generates), then get the Measure tool (under the Eyedropper) and click-and-drag it along the first edge. Release the mouse when you reach the end of the edge. Then hold the Option key (PC: Alt key), click on the end of the first line, and continue on in a different direction. You'll notice that another measurement line appears. Now, look up in the Info palette and you'll see your two measurements listed under D1 and D2.