A rack system that is configured to allow the omission of cross bars. The cross bars can be easily removable and replaceable or can be adjustable along a length of the rack system. In some configurations, the rack system includes at least one side support arrangement comprising a first vertical support and a second vertical support. Two or more side support arrangements can be provided on each side of the truck bed. Pairs of support arrangements on one side of the truck bed can be connected by one or more longitudinal supports. Accessories, such as tool boxes or gas cans, can be connected to the one or more longitudinal supports.