User blog:Son of God-Enel/Assassin's Creed 2: Trying to equip the throwing knives

Sorry if this isn't the right place for a question, but I have, well, a question.

I'm playing Assassin's Creed 2 and I'm trying to equip the throwing knives. I have a full thing of knives and I'm able to equip them from the inventory wheel no problem. But I want to auto-equip them to Left on the Directional Pad (just like the Hidden Blade is Up and the Sword is Right), and the game won't let me.

It's been a long long time since I played this game (I just got the DLC now) so I can't remember for the life of me. What am I missing?