Duplicate and overlapping objects waste ink and mean that your drawing isn’t accurate. However, often, they’re invisible.
The OVERKILL command, part of Express Tools, can help. This command deletes duplicate objects and goes further to combine overlapping lines and arcs. However, it’s not on the menu, toolbar, or ribbon, so you have to type it on the command line. For that reason, many people don’t know about it. (Update: As of AutoCAD 2012, this command is part of core AutoCAD. and is now on the ribbon. Go to the Home tab, Modify panel, and expand it to find the button.)
When you start the command, the next prompt is Select objects: and you can type all and press Enter to apply the command to the entire drawing. Then press Enter again to end object selection.
The Overkill dialog box opens.
To keep the default settings, just click OK. If there are duplicate or overlapping objects, you’ll see a message like this:
1 object(s) deleted.
You can specify lots of settings to control the process. For example, you can check the Ignore LAYERS check box to delete overlapping lines, even if they are on different layers.
The Numberic Fuzz text box determines how exact two objects must be to be considered duplicates. The default, 0.000001, deletes almost exact objects. You can change this to 0, to delete only objects that are exactly on top of each other.
The PLINES check box, on by default, removes duplicate line or arc segments within a polyline, or lines and arcs that overlap a polyline. If you uncheck this, the command only removes duplicates of entire polylines.
The OVERLAP check box, also on by default, combines objects that partially overlap into one object.
The END to END check box combines objects that don’t overlap, but are end to end, such as two colinear lines with one common endpoint.
Click OK to execute the command.