The Trim command can be used to trim a part of an object. In order to trim an object you must draw a second object which forms the "cutting edge". Cutting edges can be lines, xlines, rays, polylines, circles, arcs or ellipses. Blocks and text cannot be trimmed or used as cutting edges. The illustration on the right shows the Trim command in action. The red square and circle have been drawn using the Polygon and Circle commands respectively. In order to trim these objects, a line has been drawn (cyan in the illustration), this forms the cutting edge. The Trim command, unlike most other modify commands requires that two separate object selections are made. The cutting edges are selected first (there can be one or more) and then the objects to be trimmed are selected. In the example above, the line is selected first because it forms the cutting edge and then the square and circle are selected.
The Trim command is slightly more complicated than many other modify commands. To get a better understanding of how it works, draw a square, circle and line as illustrated above and then follow the command sequence below. Don't forget to watch the AutoCAD command line at each stage of the process.
Current settings: Projection=UCS Edge=None
Select cutting edges ...
Select objects: (select the cutting edge, P1)
Select objects: (to end cutting edge selection)
Select object to trim or shift-select to extend or [Project/Edge/Undo]:(pick the part of the square which you want to trim, P2)
Select object to trim or shift-select to extend or [Project/Edge/Undo]: (pick the circle, P3)
Select object to trim or shift-select to extend or [Project/Edge/Undo]: (to end)
Notice that at each trimming step you are given the option to undo the previous trim. This can be very useful if you inadvertently pick the wrong object.
In the above example, when the objects were trimmed, both pick points were made to the right of the cutting edge, resulting in the removal of that part of the objects to the right of the cutting edge. Obviously, the portion of square and circle to the left of the cutting edge could have been removed by picking to the left of the cutting edge. Also, you may not have noticed it, but by trimming a circle you have created an Arc object. This makes no visible difference but the object type has changed.