This is the most important aspect of permissions. You need to understand this to properly work with them. There are three different values that a permission can take:
YES will allow a permission setting unless it is overwritten by a NEVER.
NO will be disallow a permission setting unless it is overwritten by a YES.
NEVER will completely disallow a permission setting for a user. It cannot be overwritten by a YES.
The three values are important as it is possible for a user to have more than one set of permissions for the same setting through multiple groups. If the user is a member of the default "Registered Users" group and a custom group called "Senior Users" you created for your most dedicated members, both could have different permissions for seeing a forum. In this example you want to make a forum called "Good old times" only available to the "Senior Users" group, but don't want all "Registered Users" to see it. You will of course set the Can see forum permission to Yes for "Senior Users". But do not set the permission to Never for "Registered Users". If you do this, "Senior Members" will not see the forum as the Never overrides any Yes they have. Leave the setting at No instead. No is a weak Never that a Yes can override.
Figure 1.8. Manual permissions
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