Sword kit?

[LordBlade]

So I bought base kits for various weapons from the vendor on the beach in the first zone.
I've just found Sword Kit Part II: Hilt.

How do I use it to improve the base sword kit? I tried straight up combining them, and I'm told that's invalid.

[PiJäi]

You need to find "Sword Kit Part I: Guard" first (revisit the locations you already have been or look for guides) and combine it with the base sword via the crafting menu (crafting skill required). Afterwards, you can combine the upgraded sword with your Sword Kit II in the same manner

[rn_archl0rd]

By the time you find all the parts you will have found or crafted better. I don't bother with the kits for that reason.