The Extend tool allows you to quickly extend lines and arcs to other lines or arcs, until they intersect, at the click of a button. Simply select a line or arc, choose the Extend tool, select a selection and then choose the line, arc, curve or shape you wish to extend the original line to. The line will now reach intersect with your seection. If you have multiple lines to extend to the same line you can do that in the same way. You can also extend to a reference line that you will be prompted to draw once that option is selected.