But before you try this method, I recommend you to see this video first.
BUG Cara Trade Item yang Untradable (Terikat) Ragnarok Online 2 - YouTube
BUT DONT COMPLAINT YET, Since this is a wrong method, but at least it will give you some hints to do this bug... Somethings that you must know about this bug was.... Vendor system in RO2 will prevent you to moving item in your bag/inventory. Since the vendor system analyze the item not from the item ID but ITEM LOCATION IN YOUR BAG... Which mean, If you wanna bugging this system you must find a way to MOVE a Non-trade (bound) item to tradable Item when you start vending them.
What do you need to do this :
1. Some Bound Item
2. Some Tradable Item
3. Friend beside you
Step by step :
1. Target your friend before you doing anything.
2. Press Y button to start vending, place your tradable item in your vending list.
3. After name your vendor chart, ask your friend for a Trade Request. BUT TELL YOUR FRIEND TO DON'T DO ANYTHING BEFORE YOU START VENDING.
4. Start vending and IMMEDIATELY PRESS B Button, and ask your friend to abort/refuse the Trade Request.
5. This step will indicate your bug process will success or not. If it doesn't success when your press B to access your bag, you can't move your items in your bag, since system frame prevent you to do that.
6. When it success, when you press B, you can move the Items inside your bag. Then? It's easily just move your Bound/untradable item at the location of Tradable item on vending list. And WALLA.... you can sell a Bound Item. In the end, you can ask your friend to ensure that your process done in the right way.
Sometime this method fail in at 4th step. I don't why this happen, maybe the system prevent it. But don't worry since I know how to "fix it". When you find you fail at the 4th step, just ask your friend a Trade Request and trade something. Then repeat the process. I bet it will works.
Recommendation to you after knowing this method...
PLEASE, DON'T SELL ANYTHING RIDICULOUS.... Like 10 Days Card Album, 7 Days VIP Membership, Nippy Peco Ride Pet, Assassin Scroll or Wind Elixir. I know it can brings you some cash but those things is really something to say. Try to sell Bound Gear like RHD Gear or Rare Gear from Rear Boss Drop List. I tell you this 'cause good gear is essential for running some dungeon, especially Raid Map like PvE Arena and Baphomet garden. It's not only give you some cash, but also helping other player to build their character stronger than before.
That's all folks, but I tell you... I'm not responsible if anything happen after I inform you this. I tell you this is a BUG, if the Administrator of RO2 find you misuse this bug... You will know what they will do to you....
Just like my signature below, don't use this bug to be a GOD-Like Player... Just play and enjoy it... Then we're cool, okay my bro....