A scribe (writer) is allowed for candidates with benchmark disabilities who cannot write the exam themselves.
You must usually opt for a scribe while filling the application form and submit a disability certificate in the prescribed format.
Some bodies let you bring your own scribe; others arrange one — the notification states the exact rule.
The scribe must generally be from a different academic background than the subject of the exam.
Extra compensatory time is also given along with the scribe as per the rules.
Apply early — scribe requests made after the form closes are rarely accepted.