Editing Access Masks 
Access Masks are not valid in vBulletin 5. They are maintained to show permissions from older versions
Path to Access Mask Manager: Users > Access Masks

Although membership in multiple groups is a good way to create exceptions to rules set up by usergroup permissions, they might be too powerful for some situations. For cases where you simply want to give a specific user access to a forum that he or she wouldn’t normally have access to, an alternative solution is access masks, which override all forum-level usergroup permissions.
Access mask settings have no effect unless you have enabled access masks in vBulletin Options.
You must click Save for changes to take effect.
To edit the access masks assigned to a specific user, go to Users > Search for Users. Then search for the user you want to edit and click Edit Forum Permissions or Edit Access Masks.

To view existing access masks, go to Users > Access Masks.

Access masks work similarly to forum-level usergroup permissions: inheritance to child forums still occurs. However, you do not have as many options as with a forum permission:
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