Abstract: An extendable support mechanism for a cargo bed of a pickup truck or the like. One or more support members are attached to opposite sides of the cargo bed and adapted to be positioned vertically upwardly from the cargo bed in order to support a tent-like structure or an object which is also positioned in part on the cab of the vehicle. Preferably, three tubular support members are provided in the support mechanism. Each of the tubular members are comprised of two telescopic members and are extendable in order to vary the height of the support member in the vertical direction in order to be used to hold members on the top of the vehicle. The support mechanism can be attached to an articulating bracket member which allows the support member also to be used as a cargo bed extender when desired, and also to be rotated to a stored position inside the cargo bed. In an alternate embodiment, the support members are held in vertical position on the sides of the cargo bed by fixed bracket members.