You can possibly lock your opponent's monster zone if he/she has no tribute monsters. Use Floodgate Trap Hole when your opponent Summons a Monster. Then disable the 2 remaining zones by using Ojama Knight's effect. You can then wait to get the cards that you needed or burn your opponent.
The text "monster(s)" on Floodgate Trap Hole means that it can affect multiple cards. See these screenshots below for example.
Today I beat some whale who has 3 of this cancer, with him having successfully having used all 3 on me during the duel. That felt great. An UR in a large box that's like the second worst of the game, and there are people who have 3... what the hell is wrong with the world. Whoever I see using more than 1 of this, be ready to have one hell of a tilt duel as I will pull the most cancer tactics possible.
If you are f2p and have 3 of THIS out of all big box UR you're as terrible as p2w jerks. With limited resources you should focus on big box URs that are monsters, since monsters are what makes the game. 3 of this card = you dedicated all your resources to a big box with 2 or so good monsters and the rest of all cards are absolute garbage. You made a big effort for the most cancerous trap ever.
You were doing good there.....until the last sentence. Now it sounds more like you're just salty some players have 3 copies for free, just by using gems.
Personally sick and tired of this card being used in random decks to win via deck out. 2 floodgates = win through stall regardless of your deck provided you have more cards in your deck than your opponents (which is usually case for the player as they are behind and have no proper way of winning). BS, same reason WoD shouldn't be in this game...