Corrugated liner or 2 Ply liners are basically wavy sheets made from 2 rolls of kraft paper.

Generally used as an additional layer of protection to prevent scratches on product, to prevent dust or direct sunlight exposure during its transit.

They’re great because they're, lightweight, and can be made in different sizes and shapes to fit different needs where shape of product is irregular.

They not only solve the intended purpose but are highly versatile and cost effective at the same time.