How Protect item works?

I am soon making a pure/zerker and im wondering how protect item works...
I used to think that it protected your best item in your inventory but i guess i was wrong.
When i used to BH, i had Magic Robe (G) in my inventory and i equipped a rune axe, i put protect item on and died keeping my axe...
About 5 minutes ago, i watched someone dying with claws and fury and i noticed he kept his fury instead of D Claws.
Could someone please explain how this skill works cause i'm quite scared of losing my items atm.

 

Goes on low alch price + you cant use prot item in non +1 worlds.

 

Ohh.. ic tyvm.

 

Just a little side note: I thought items were protected the item based on High Alch values? so Protect +1 would protect the next highest valued item in your inventory