You can extend entities so that they end at a boundary defined by other entities. You can also extend entities to the point at which they would intersect an implied boundary edge. When extending entities, you first select the boundary edges, and then specify the entities to extend. Using this you can extend the line, arc, spline and polylines. To use this choose 'Extend' tool from Modify menu bar or select icon from Editing Toolbar.

Steps to Extend Entity :-

Fig. 1

Fig. 2

In above fig. rectangle is reference entity whose edge is consider as boundary edge and other two entities, lines are extended upto that oundary. For both entity there end part is selected to extend it.

Also if boundary edge is not present in front of the end part of entity to be extend then it remain as it is i.e. It will not extend.

See Also