Business Insider last Friday obtained Apple’s 22-page document for internal distribution, titled “Visual/Mechanical Inspection Guide,” that explains how iPhone service eligibility is determined while specifically highlighting what is and isn’t covered in warranty repairs.

Dated March 3, 2017, the internal guide covers all iPhone 6, iPhone 6s and iPhone 7 models though a similar document exists for all of Apple products.

Although Apple’s standard warranty covers incidents such as broken pixels, debris under the display glass, misaligned FaceTime camera foam and a single hairline crack on the front glass, other types of damage may require an out-of-warranty repair.

But how does Apple determine what an eligible repair is?

The guide says that technicians are required to visually inspect a device for signs of physical damage and talk to the owner to determine if liquid damage may have occurred.

The document reveals that Apple might swap the phone under warranty even if an external liquid indicator has been tripped, assuming there are no other signs of damage.

Out-of-warranty replacements are provided for LCD fractures, cameras damaged from lasers, display cracks at a point of impact, a bent or split enclosure, damaged components like Lightning, audio or mic parts, extreme abrasion and liquid damage confirmed by the user.

An Apple technician told the publication that the guide is used for training, to teach service technicians how to inspect devices for physical damage and determine cost for damage.

Service technicians don’t refer to it all that often unless there’s an “oddball issue.”

In other instances, the owner whose device’s screen suffers from dead pixels has to specifically ask for it to be fixed. Cosmetic damage like enclosure wear, housing dents, chips and pitting, scratches and scuffs or chassis brightening is not covered by the warranty.

According to Apple’s FAQ, damages stemming from “accident, disassembly, unauthorized service and unauthorized modifications”, like using an unofficial battery or submerging a phone in water, are not covered by the one-year warranty.

“There are always those one-off issues that the phone is technically not covered under warranty but we swap the phone anyways under warranty,” said one Apple retail employee.