CG 20 37 grants additional insured status for completed operations, protecting the GC against claims that arise after a sub has finished and left the site. Paired with a CG 20 10, it closes the gap between active work and post-completion exposure.
For projects with long-tail risk, structural work, roofing, anything where a defect might appear months later, requiring both endorsements is best practice. Confirm the completed operations coverage extends for an adequate period.