Move Object to the side of the Screen

I am working on making a mobile phone game and need to have a wall at each side of the screen. To get around the issue of different screen sizes I was going to move the wall to the left/right side to the camera.

Using this code

 camera = GameObject.Find("Main Camera");
 cam = camera.GetComponent<Camera>();
 
 transform.position =  cam.ScreenToWorldPoint(new Vector3(0,0,0));

I assumed it would move the object to the bottom left of the screen, but it isn't working. It ends up moving it to the right slightly.

Any tips or help would be great.