All objects in the ADE display have a Lock Status.  Some types of object can be edited by the user and others are not editable.  The easiest way to tell is via the Tool Tip.  A yellow background indicates an element that is not locked in any way. You can move, delete, and edit this element as you wish. Elements with this status are compiled into the bgl file.   This is a lock status of None

Locking and unlocking will work only on objects that have a lock status of None or User Locked.  The easiest way to change the lock status of an object is via the right click menu

I have selected this parking space and because the too tip is yellow I know that it is not locked.  If I now Right Click I can change that lock status

The Lock Menu entry in the Right Click Context menu is not checked - so to lock the object I just click that entry.  Now when I check the tool tip I see it is pink so the object is locked

If I deselect the parking space and select it again.  I find

1. the selection color is now pink also.  That it another way to know the object is locked.
2. In the Right Click Menu I can now see the Lock Object menu entry is checked.

Individual objects can also be locked/unlocked via the Object Property Dialog

You have the choice whether to allow editing of locked objects or not.  Locking will always stop an object being dragged.  It will also stop it being accidentally deleted.  Try to delete a locked object and you will see a warning and the object won't be deleted.  However you still might want to edit the properties of the object.  Open the Options Dialog by using the Settings Menu and then Options.

On the General Tab is a checkbox called Locking Disables Editing.  If this is checked then you will not be able to edit locked objects.  This applies to all locked objects.  You can't decide whether to allow editing on an object by object basis.  It is checked in this case so if I try to edit a locked object I should not be able to

In the Right Click Menu Edit Object is not there and Double Clicking the object or using the Enter key has no effect.  If I un check the option in Settings and Right Click again I now have the Edit Object option

Sometimes you might want to lock a whole group of objects and you can do this via the Lock Menu

This lets me lock all the aprons and so on.  Locking, for example. Aprons will lock all the aprons at the airport.  You can easily try this.  It is just a group lock so you could select an apron and individually unlock it again.  Now all the aprons will be locked except the one you just unlocked.  Finally you can unlock the same groups vie the Unlock Menu

If you click the Aprons option then all aprons that are locked will be unlocked.  Aprons that are already unlocked are left alone.  The end result is that all aprons will now be unlocked.