What is Google Webmaster Tools owner access and how to provide one?

Google Webmaster Tools Full access is not equal to owner access.
To Add an owner

1. On the Webmaster Tools home page, click Manage next to the site you want, and then click Add or remove users.
2. Click the Manage site owners link.
3.  In the Verified owners section, click Add an owner.
4. Type the email address of the owner you want to add, and then click Continue.