My old boss had one of these on our work truck... sealed really well and came open for full bed access REALLY easy. It doesnt have snaps, It closes like a zip-loc bag. We fully opened and closed that lid 2 or 3 times a day and it was quick and easy. We called it was the zip-loc cover. If I ever buy one for my current truck, it will be one of these.
http://www.tonneaucoversworld.com/ex...1973-1987.aspx