cloudduster on "How to find the menu [slug] item"

I'm trying to add a login/logout link in my nav bar; thanks to this:

http://wordpress.org/support/topic/log-in-and-logout-link-in-top-nov-menu?replies=2

However, I need to find the value of the [slug]

wp_nav_menu_[slug]_items

Where can I find this? I have 2 menus, and want to show the link in the top menu.