Select the Line Tool from the Object Toolbar (or use the keyboard shortcut <b>F3</b>, or the menu <b>Object → Curve → Line</b>).
<table><tr><td>[[Image:fdtd_lec1_7_toolbarlineMOMTUT3 5.png|thumb|center|800px750px|Selecting the Line or Circle tools from [[EM.CubeLibera]]'s Object Toolbar.]]</td></tr></table>
With the line tool selected, click the origin (0,0,0), and drag the mouse to start drawing a line. While still in “Draw Mode”, press and hold the <b>Alt</b> button of the keyboard. This forces the drawn line to be constrained along the alternate Z-axis (normal to the default XY plane on which the mouse pointer moves). Observe the changing Length value in the dialog box as you drag the mouse back and forth. When the length reaches a value of 150 units, left-click to “lock-in” the value. You may also left-click at any point and adjust the length by typing in a value of 150 in the object’s property dialog.