Define a custom role
Create a custom permission set for a particular item
Sometimes it is easier to grant certain permissions locally to someone for a content item, without saving this permission set as a new generic role. In this case, when granting Access, select Custom from the pop-up, then click Save.

The Detail page will automatically open and you will be able to pick the necessary permissions as part of a custom role for the selected user/group (see below).
Grant or revoke a permission
From the Details view of a user or group:
Click Edit on the header to make the Custom role appear.


Click once in the checkbox to grant the permission
Click a second time in the checkbox to revoke the permission.
Click Save to store your changes.
If a permission has been revoked, then it cannot be re-granted again at a lower level in a hierarchy.