Create and modify 3D models > Create 2D geometry > Change 2D geometry > Untrim 2D geometry
  
Untrim 2D geometry
The Untrim Geo command untrims geometry that has been trimmed with, for example, the Trim Extend commands. The geometry is untrimmed to infinity.
To untrim 2D geometry,
1. Click Modeling and then, in the Modify 2D group, click More.
2. Click Convert Geo to Infinite in the Tools section.
3. Click the geometry to untrim.
4. Click OK to complete the operation.