How to disable sliding on a 2d object?

Question

Unity

The object moves through it.
rigidbody2D.velocity
I tried to set the physical material and set it to 1, but it doesn’t work anyway

Answer 1

private void Update()
    {
        rigidbody2D.velocity = new Vector2(speed, rigidbody2D.velocity.y);
        if (leftPos != leftBttn.transform.position.y)
        {
            //rigidbody2D.velocity = new Vector2(speed, rigidbody2D.velocity.y);
            speed = -5f;
        }
        else if (rightPos != rightBttn.transform.position.y)
        {
            speed = 5f;
        }
        else
        {
            speed = 0f;
        }
        rigidbody2D.velocity = new Vector2(speed, rigidbody2D.velocity.y);
    }

I made it so that when you press the button, it shifts a little down and thereby changes the position