How do i make a object be at a different objects box collider location?

Hi! it’s Šķoobi here and i have one quick question!

So i got a script from brackeys.com 2d assetpack where he made a invisible 2D boundaries it’s called GameSetup.js at the pong folder.And i converted it to C# and i wanted to do a getComponate stuff to make a 3d Box on the Invisible bourder so i don’t have just invisible walls how do i do it ?

ps : i can run the game and play it but it shows that it hasn’t place the box at its place…
Screenshot : Screenshot - 5f599d7bcb2b3005673c5375a4684281 - Gyazo

ps , ps : its a 2D game!!

Box Script

using UnityEngine;
using System.Collections;

public class CubeMoveTest : MonoBehaviour {

	public GameObject TopWall;

	private BoxCollider2D boxCollidder2;


	void Awake ()
	{
		boxCollidder2 = TopWall.GetComponent<BoxCollider2D> ();
	}

	void start ()
	{
		transform.position = new Vector3 (boxCollidder2.transform.position.x, boxCollidder2.transform.position.y, 0);

}
}

boundaries Script

using UnityEngine;
using System.Collections;

public class ScreenWalls : MonoBehaviour {
	
	
	//Reference the camera
	public Camera mainCam;
	
	//Reference the colliders we are going to adjust
	public BoxCollider2D topWall;
	public BoxCollider2D bottomWall;
	public BoxCollider2D leftWall;
	public BoxCollider2D rightWall;
	
	
	
	void  Start (){ //Only set this to Update if you know the screen size can change during a playsession.
		
		//Move each wall to its edge location:
		topWall.size = new Vector2 (mainCam.ScreenToWorldPoint (new Vector3 (Screen.width * 2f, 0f, 0f)).x, 1f);
		topWall.center = new Vector2 (0f, mainCam.ScreenToWorldPoint (new Vector3 ( 0f, Screen.height, 0f)).y + 0.5f);
		
		bottomWall.size = new Vector2 (mainCam.ScreenToWorldPoint (new Vector3 (Screen.width * 2, 0f, 0f)).x, 1f);
		bottomWall.center = new Vector2 (0f, mainCam.ScreenToWorldPoint (new Vector3( 0f, 0f, 0f)).y - 0.5f);
		
		leftWall.size = new Vector2(1f, mainCam.ScreenToWorldPoint(new Vector3(0f, Screen.height*2f, 0f)).y);;
		leftWall.center = new Vector2(mainCam.ScreenToWorldPoint(new Vector3(0f, 0f, 0f)).x - 0.5f, 0f);
		
		rightWall.size = new Vector2(1f, mainCam.ScreenToWorldPoint(new Vector3(0f, Screen.height*2f, 0f)).y);
		rightWall.center = new Vector2(mainCam.ScreenToWorldPoint(new Vector3(Screen.width, 0f, 0f)).x + 0.5f, 0f);
		
	}
}

It looks like you need to supply TopWall with a GameObject. In the editor you can drag and drop a wall into the CubeMoveTest script’s TopWall slot. This of course means you need a GameObject with a BoxCollider2D to use as a wall. Also if you want it visible you can make a sprite in a photo editing program that is either the size that you need, or stretch it with the scaling in unity to the size you need.