The Iron Pipe effect allows Sabitsuki to attack some NPCs and access hidden areas when the action button is pressed. The effect can be obtained in the Pipes and Phone Poles World.
To find it, go down from the entrance. When you see two lone pipes (one sticking up and one lying on the ground), head west towards a cluster of pipes. Interact with the rusty pipe in the middle to obtain the effect.
Go down till you reach two poles (one sticking up, another lying in the water). East from them, you'll pass a tiny house that you do not need to go through. At the top of your screen, you'll see more pipes. Go up to them and in the middle, there should be a bloodied iron pipe sticking out. Interact with it.
- The Iron Pipe effect is the equivalent of the Knife effect in Yume Nikki.
- Pressing the action button when there is nothing to interact with causes Sabitsuki to put the pipe over her shoulder.
- The effect's actual name is Iron Pipe (as evidenced here), but is commonly mistranslated as Steel pipe.
- The effect is てつパイプ in Japanese.