Tonneau

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.

In current automotive terminology it typically refers to a hard or soft cover that spans the back of a pickup truck to protect the load from weather elements or thieves, or to improve aerodynamics.

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 folding covers are more popular to truck owners as they offer better protection, security, and waterproofness.

[5] Early open-bodied touring-type automobiles used tonneau covers to protect unoccupied rear seats.

The skins covered gaping cockpits that would otherwise disturb airflow and create undue drag; as a result, tonneau-equipped cars ultimately went faster with a given amount of power.

[6] Tonneau covers are used in lieu of hard or soft convertible tops on open sports cars such as the MG, Triumph, Austin-Healey, and Porsche Boxster.

The most common style is the roll-up tonneau made from cloth or vinyl,[citation needed] which uses a rib-like structure to support the fabric and keep it taut and roll up toward the cab of the truck.

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.

[16] Many sellers claim that tonneau covers improve gas mileage because they make the truck more streamlined.