How to create a square using Linecast & loops?

I'm trying to draw a square using loops but no success so far. This is one of my many attempts:

                 for (int i = 0; i < 1; i++) {
                         Vector2 start = new Vector2 (collider.bounds.min.x + (collider.bounds.size.x * i), collider.bounds.min.y);
                         for (int j = 0; j < 1; j++) {
                                 Vector2 end = new Vector2 (collider.bounds.min.x, collider.bounds.min.y + (collider.bounds.size.y * j));
                                 RaycastHit2D hit = Physics2D.Linecast (start, end, obstacleLayer);
                                 Debug.DrawLine (start, end, Color.red, 10.0f);
                         }
                 }[