Retractable tonneaus are a viable option when you want to combine ease of bed access with the durability of a hard top. It's a great way to haul large objects without having to completely remove the cover from the bed. When you consider a fiberglass hard top can weigh upwards of 125 lbs. and necessitate 2 or 3 men to lift, the benefit is clear. Usually made of vinyl-covered aluminum or powder-coated aluminum interconnected planks, these retractable truck bed covers are like a horizontal garage door, rolling open or closed in seconds. They latch or lock at the tailgate for security. If your tailgate itself locks as well, you'll achieve a level of security that's almost comparable to that offered by a hard cover. Having said that, retractable tonneau covers do have a few features that might be seen as drawbacks. For example, some bed space up front behind the cab is sacrificed to fit the canister that holds the tonneau. Additionally, they are widely considered to be prone to leaking, but that's to be expected from any tonneaus other than the full-out hard cover. Some styles have a run-off water container that must be emptied periodically. Others have drainage tubes that route collected water out of the bed towards the ground. These tubes must be kept clear to avoid a potential back-up and flooded bed situation. However, if a little bit of water isn't going to be a huge problem for your cargo, you'll be fine with a retractable.
Preventative maintenance for retractable truck bed covers
Take care not to allow much snow or ice to build up on your tonneau, as this may stretch it out and it won't fit as tightly. Retractable tonneau covers are simply not made to withstand excessive weight from above. Also, to keep the rolling/retracting mechanism in working order, you'll have to commit yourself to at least a minimum of upkeep (lubrication, etc.) As with anything with moving parts, retractable truck bed covers can only work as well as they're maintained. If you're set on the convenience of a hard cover that can be removed single-handedly in seconds, then you won't mind the extra effort needed to upkeep your tonneau.