A 3D line is a line that locks to the isometric axes (nearest 30°) when drawn. It is usually used to create symbols or add construction lines.
To add a 3d Line:
1 Click Solid Extrusion . Right click 3D Line.
The prompt reads "Iso line start point:"
2 Click a start point for your line.
The prompt reads "Next point or enter length:" As you move the mouse around, you will notice the cursor locks to the nearest 30°.
3 Either click a point or type a distance and press ENTER.
The distance you enter will be the correct isometric distance rather than the actual 2D distance.