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. They are made of a wall of individual aluminum slats, covered with soft vinyl. In the unrolled position, these aluminum slats form a hard aluminum shell, which not only covers the cargo inside the bed, but also may support loads up 400 pounds on top of it.