The Blues

Latent Print presents Styleguide Wednesday, a post each Wednesday featuring an editorial convention from the world of styleguides. View previous Latent Print moments of stylebook study and reflection here. This week features bluelines.

What are bluelines? Bluelines is the unbound, printed document. It should be treated as the final-final, not the stage to add commas between independent clauses or to correct misspellings. Chicago 3.40: "Any correction that would involve typesetting should be avoided at this stage for reasons of schedule and expense."
My PM, not happy to create new work orders for the printer, agrees.
I've seen editors use bluelines for final line edits. With desktop software, a few last-minute changes before upload aren't a problem; however, the changes can try the patience of designers and staff as deadline hovers.
During bluelines a proofreader should search for printer error or mistakes in file transfer. Make sure the bluelines match the revised proof. Check for flashes, check borders, tables, formatting changes introduced in file transfer, check colors.
Proofreaders, as always, your comments welcome. Did I forget any bluelines procedures?