FASA Games, Inc.

Do you have to wield a Thread Item to benefit from some of it's powers? Or for some items it is more like 'thread strengthens True Pattern' kinda thing like weaving threads through pattern items to others?

I've always interpreted it as being dependent on the intent behind the power. For example, the ranks on a Thread Wand that increase your Spellcasting aren't going to work unless you're actively including it with the casting. The ranks that increase Spell Defense, on the other hand, should work as long as you just have it on your person, as that's much more of a passive bonus.

The rules indicate that you must be carrying it around. This is to make it clears which person who has a thread woven is benefitting at the time. From there, I would go with the text. The items usually dictate how you must be interacting with it. Wielder means it must be in your hand. Wearer that it must be worn, not simply carried around. Owner that it is stashed somewhere on you person, or near you (thread boats, carpets, pillars, etc). All of this is, of course, subject to what a particular thread item indicates as well as your preferences as GM.