False.
A heavy rough line at the bottom of a bottle does not necessarily indicate that the bottle is prepared by compression molding. The presence of a rough line at the bottom of a bottle can be caused by various manufacturing processes, including blow molding, injection molding, or even the use of a mold insert. The appearance of the bottom line can depend on factors such as the design of the mold, the material used, and the specific manufacturing techniques employed. Therefore, the presence of a heavy rough line alone is not sufficient to determine that compression molding was used to prepare the bottle.