A tonneau ( or ) is an area of a car or truck open at the top. It can be for passengers or cargo. A tonneau cover in current automotive terminology is a hard or soft cover that spans the back of a pickup truck to protect the load or to improve aerodynamics. Tonneau covers come in many styles that fold, retract, or tilt open, and can be locked shut. Common materials used include steel, aluminium, canvas, PVC, fibreglass, and carbon fibre. Tonneau covers are also used to cover and protect open areas of boats. Many of these covers are made of waterproofed canvas and are held in place by snaps. The older, original tonneau covers were used to protect unoccupied passenger seats in convertibles and roadsters, and the cargo bed of a pickup truck or coupé utility. Hard tonneau covers open by a hinging or folding mechanism while segmented or soft covers open by rolling up or folding. Truck and car tonneau covers keep items out of the sun and out of the sight of potential thieves. Origin A tonneau was originally an open rear passenger compartment, rounded like a barrel, on an automobile and, by extension, a body style incorporating such a compartment. The word is French, meaning 'cask' or barrel, cf. “tun”. Rear entrance tonneau Early tonneaus normally had a rear-facing hinged door, but single and dual side doors were soon introduced. When the street was muddy or dirty, the car could be backed up to the curb so tonneau passengers could exit directly onto the sidewalk. Truck use and styles Tonneau covers are used in coupé utility cars and pickup trucks to cover and secure the cargo tray and come in a variety of styles. Mainly they are categorized by material Soft or Hard covers. Soft covers can be rollup or folding and Hard covers are rollup, folding or one piece. The most common style is the roll-up tonneau made from cloth or vinyl, which uses a rib-like structure to support the fabric and keep it taut. A snap-based system is also used, but has become less common due to truck owners not wanting to install the snaps on their vehicle as they typically require drilling or permanent adhesive. Roll-up tonneaus are opened by rolling the cover up toward the cab of the truck. Hard roll-up tonneau covers are more firm than regular roll-up tonneau covers.