How to Lock your Bootloader back to LOCKED
This guide will help you lock your bootloader and have it say LOCKED. In order to do this you MUST BE S-Off. If you are still S-On and would like to do this then you need to gain S-Off first. See my guide for gaining S-Off HERE.
There are few different way to do this. The easiest way is to use the Guru Bootloader Reset Tool. It is simply flashed in recovery. See HERE.
If you used revone to gain S-Off or still have an older hboot you can use this toolkit to use revone to Lock your bootloader:
The generic method to reset the Bootloader back to LOCKED on any hboot regardless of how you gain S-off is outlined in this XDA thread:
** Note that this method requires root. You will have to install Superuser. Instructions in the thread. If returning phone after you lock, you should delete the superuser.apk from the /system/app directory on you phone after you are done re-locking.