Futhork items are either futhork runes or futhork equipment that is socketable.

A Furthork item has a 2% chance to drop after killing a mobile.  The futhork
item level will be the same level as the mobile.

A futhork equipment item will have either one, two or three sockets.

A futhork rune when fused to a futhork item will take up an item socket but
give the value of the rune to the equipment.  example: a level 10 damage rune 
will add 10 damage to your EQ.

fuse is to take a futhork rune and put it in a futhork item socket.

You can only fuse a rune that is equal or lower level then the futhork item 
you want to fuse it in to.

fuse damage dagger, would fuse a damage rune into a futhork dagger.