Extends objects to meet the edges of other objects.

Button
Ribbon: Home tab
Modify
panel
ExtendNot available on the ribbon
in the current workspace
Menu: Modify
ExtendNot available in menus
in the current workspace
Toolbar: Modify
To extend objects, first select the boundaries. Then press Enter and select the objects that you want to extend. To use all objects as boundaries, press Enter at the first Select Objects prompt.

The following prompts are displayed.
Current settings: Projection = current, Edge = current
Select boundary edges...
Select objects or <select all>: Select one or more objects and press Enter, or press Enter to select all displayed objects
Select object to extend or shift-select to trim or [Fence/Crossing/Project/Edge/Undo]: Select objects to extend, or hold down SHIFT and select an object to trim, or enter an option
Trims the selected objects to the nearest boundary rather than extending them. This is an easy method to switch between trimming and extending.
Selects all objects that cross the selection fence. The selection fence is a series of temporary line segments that you specify with two or more fence points. The selection fence does not form a closed loop.