AutoCAD Tip: Trimming or Extending elements to Xref boundaries

By Dennis Collin

Recently I had a question from an AutoCAD customer about the prospect of trimming an element to an element within an External Reference File (Xref). An external reference file is like a block linked to the original file so that if that file is changed the reference file will update within its host drawing when reloaded.

A common use of an Xref is to overlay a site drawing to help position services and occasionally a line needs to be extended or trimmed to a road edge or boundary line. In the past this functionality was provided by the old Express tools Btrim and Bextend, but some time ago the standard Trim command was improved so that not just blocks could be selected as boundaries but elements within Xrefs could be used as well.

Whilst block elements can be selected individually, Xref elements need to be selected with a crossing method (Window/Polygon/Lasso). Once selected, click on the element to extend or trim as normal.

N.B. For best results ensure Trim’s Edge mode is set to No extend (default setting).