Keyguard has to be one of the most frustrating commands in game. It works on some areas fairly well but in other areas (such as grocery items) it is near impossible to use effectively.
This command guards a particular item (or stack of items) from being pulled into the keys when you do a fill from pack. I've noticed an issue with the grocery items where if you take one of the stack away the guard no longer protects the remaining stack. This means you have to go back into the key to pull out food for pets or yourself.
Another example of this is when you pull out additional band aids to put on a bio you must move your personal stash from you main pack to somewhere else so as not to 'overwrite' the item id of the stack you're using for yourself. While it is something you can always work around it also is something that seems to have a simple solution as well.
If possible, my suggestion would be to have the guard work on an item type rather than and item ID. this would mean that a bulk fill would leave all of a item type alone in a pack. One keyguard would keep it that way until revoked by the player.
Regards,
Kaw...