A lift and pivot hinge mechanism that can be installed upon a conventional pick up truck bed in conjunction with a conventional box type cargo topper. The lift and pivot mechanism opens the topper in a clamshell manner whereby the rear of the topper is elevated in relation to the truck bed, thereby providing greater access to the cargo area. The opening process is accomplished in two stages. The topper is first slightly lifted diagonally, further defined as horizontally relative to the truck bed and rearward in relation to the passenger cab. By performing this first step the necessary clearance is provided to perform the second step, which is pivoting the rear of the topper upward in relation to the truck bed thereby providing greater access to the truck's cargo area. Alignment guides are utilized to assure consistent placement of the topper in relation to the truck bed. The hinge mechanism may be utilized with conventional (non-purpose built) truck toppers, does not occupy precious cargo area within the truck bed and can be fitted to all presently known pick up truck beds. One or more linear power assist mechanisms are utilized to assist in the opening and closing process.