This command is available in the expanded Draw panel in the Home tab, as shown:

Construction Lines are infinite lines that are helpful when you make lines for reference. An example of a reference line is a construction line made using the reference of a floor plan to make the elevation. In the following figure, the red lines are Construction Lines:

Using these red lines, you can make another drawing that exactly aligns with the floor plan shown here. Make a note here that I have used a red color for the construction line to make them look distinct but in general, the construction lines take the default drawing color.

In the following example, I will show you the steps to make a construction line:

1. To make a construction line, select the tool from the expanded Draw panel of the Home tab or use its command, XL.
2. Now, click on a point to specify the first point of the line and then click on another point in the drawing area to specify the direction of the construction line.
3. As mentioned earlier, construction lines are infinite lines and no matter how much you zoom out, they will always appear to extend on both sides. You can, however, trim your construction line to make it of finite length and in doing so, the construction line turns into a simple line.

In the following figure, I have trimmed the construction line using the circle as a reference and the resulting object is a line:

As you may have noticed, you can use construction Lines to aid the drawing workflow but when these construction lines are converted to a finite length, they become normal lines and so can be used directly in the drawing, too. The next draw tool that we will discuss in the next section is unlike all the other draw tools that we have discussed so far. This tool is called revision cloud and it is only used as markup in a drawing and it is usually removed from a drawing when the drawing markups are addressed.