Lowe's does not carry Masonite sheets. Masonite is a type of hardboard formed using a non-formaldehyde-based process to create a hardboard that is smooth only on one side. Lowe's carries hardboard in several forms, including pegboard, smooth and decorative forms.
Pegboard sheets, from manufacturers DPI, Triton Products, and Threedwall, are available in 2-by-4-foot; 4-by-4-foot and 4-by-8-foot panels. Decorative hardboard is available in wainscoting, brick-look, V-groove and embossed bamboo in various patterns, including squares, swirls and stars, among other designs. Smooth hardboard is available in 47.75-inch-by-7.98-foot panels. The fasteners and other tools necessary to work with hardboard are also available from Lowe's.