When you are building a loop and you are in the edit mode, you can choose to lock a hub. Open the hub panel and in the list at the bottom you will see a padlock and it says Unlocked. Click the lock and you will see your options. Click the padlock if you want to lock the hub to make your students unable to see any of the content until you unlock the hub for them. Click the eye if you change your mind. Notice that all hubs after the one you have locked, will also be locked for your students. When you unlock the one you padlocked, the following hubs will also be unlocked.This means that if you want to be able to open one hub at a time while working in the loop, you must put a padlock on each hub.