How to Use the TRim and EXtend Commands in AutoCAD 2014 - dummies

How to Use the TRim and EXtend Commands in AutoCAD 2014

By Bill Fane, David Byrnes

TRim and EXtend are the twin commands for making lines, polylines, and arcs shorter and longer in AutoCAD 2014. They’re the yin and yang, the Laurel and Hardy, the Jack Sprat and his wife of the AutoCAD editing world. The two commands and their prompts are almost identical, so the following steps cover both.

  1. Click the Trim or Extend button on the Home tab’s Modify panel.

    AutoCAD prompts you to select cutting edges that will do the trimming (or, if you choose the EXtend command, boundary edges for extending to):

    Current settings: Projection=UCS, Edge=None
    Select cutting edges ...
    Select objects or <select all>:
  2. Press Enter to accept the default option to select all drawing objects, or select individual objects by picking them. Press Enter to end the object selection.

    The objects you select become the cutting edge of the TRim command or the boundary to which objects will be extended by the EXtend command.


    AutoCAD prompts you to select objects that you want to trim or extend (EXtend doesn’t have the eRase option):

    Select object to trim or shift-select to extend or [Fence/Crossing/Project/Edge/eRase/Undo]:
  3. Select a single object to trim or extend. Choose the portion of the object that you want AutoCAD to trim away or the end of the object that’s closer to the extend-to boundary.

    AutoCAD trims or extends the object to one of the objects that you selected in Step 2. If AutoCAD can’t trim or extend the object — for example, if the trimming object and the object to be trimmed are parallel — the command line displays an error message such as Object does not intersect an edge.

    You can select multiple objects to trim and extend by typing F and pressing Enter to use the Fence object-selection mode or by entering C to use a crossing selection. Even better, you can use implied windowing and drag a selection box to select multiple objects.

    The command line continues to prompt you to select other objects to trim or extend:

    Select object to trim or shift-select to extend or [Fence/Crossing/Project/Edge/eRase/Undo]:
  4. Choose additional objects or press Enter when you’re finished trimming or extending.

    Here’s a triple-threat tip: If you accidentally trim or extend the wrong object and you’re still using the TRim or EXtend command, type U and press Enter to undo the most recent trim or extend operation. You can switch between TRim and EXtend without exiting the command by holding down the Shift key.

    And, finally, if a remnant won’t trim because it doesn’t cross the cutting edge, type R (for eRase) and press Enter to erase it without leaving the TRim command.

Another common use of the TRim command is to trim out a piece of a line between two cutting edges. In the two-cutting-edges scenario, TRim cuts a piece out of the middle of the trimmed line. The default option for selecting cutting edges or boundaries is <select all>, which works well in this scenario.

Pressing Enter to accept the default option selects all objects in the drawing as a cutting edge if you’re using the TRim command, or a boundary if you’re using the EXtend command.

An object being trimmed or extended can also be a cutting edge or extending boundary, and vice versa, all in the same run of the command.

The LENgthen command provides other useful ways to make lines, arcs, and polylines longer (or shorter). You can specify an absolute distance (or delta) to lengthen or shorten by, a percentage to lengthen or shorten by, or a new total length. Look up the LENgthen command in AutoCAD’s Help system for more information.

LENgthen is an option on the grip pop-up menus on lines and arcs. To display the menu, just hover the mouse pointer over an endpoint grip on either of those object types, or over one of the new triangular grips on an elliptical arc, and click Lengthen.