You will note the round shape of the spring is some what raised on one side. Insert the spring so that the spring is raised in the Center. ... Toward you ...then be sure to insert the small clips in the outer edge of bobbin case. Also rotationally be sure the flat portion of spring is configured in the same position as the shape of the opening of the bobbin case It's purpose is to put pressure on the bobbin and control back lashing or spinning of bobbin