Overlay Versus Attach in a Nested Reference Chain
A project has three drawings: SITE.dwg, BUILDING.dwg, and SHEET.dwg. BUILDING references SITE as an xref, and SHEET references BUILDING as an xref. The drafter wants SHEET to show the building and its site context, but does not want SITE to appear twice when BUILDING is later referenced into a fourth drawing, MASTER.dwg, that also references SITE directly. SITE.dwg is also being edited by another team member, and the drafter needs to work on SHEET today without waiting for those edits. Currently SITE is attached (not overlaid) in BUILDING.
1. Recommend the reference type for SITE in BUILDING and explain the effect on SHEET and MASTER.
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SITE should be changed to an overlay in BUILDING. An attached xref is included in the host drawing and is also passed along when that host is itself referenced; an overlay is included in the host but is not passed along to drawings that reference the host. With SITE overlaid in BUILDING, SHEET (which references BUILDING) still displays SITE through BUILDING's reference, because the overlay is visible in the host. MASTER, which references both BUILDING and SITE directly, will show SITE once from its own direct reference and will not receive SITE through BUILDING, avoiding the duplicate.
The change is made in the External References palette by selecting SITE and switching its type from Attach to Overlay, or by re-referencing SITE with the Overlay option. The drafter should then reload and verify in both SHEET and MASTER.
2. Describe how to proceed with work on SHEET today given that SITE is being edited, and the risks of each option.
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Options: (1) Leave SITE referenced and accept that SHEET shows the last saved version; the drafter can reload when the other team member saves, but any work done against a stale site may be wrong. (2) Bind SITE into BUILDING, which converts it to a local block; this removes the dependency but breaks the live link and creates a divergent copy that will not reflect later site edits. (3) Use a copy of SITE saved with a dated name for today's work, then swap back to the live reference before issue.
For a same-day working session, option 1 with a note to reload before plotting is usually safest because it preserves the live link. Binding should be reserved for archival or deliverable snapshots, and if used, the team should record that the bound copy is frozen. The drafter should also confirm the xref path is relative so the reference resolves on other machines.