A check strap assembly for a pickup truck tailgate may include a truck bed, a tailgate, and opposing side panels. The tailgate is mounted to the truck bed for pivotal movement. The opposing side panels are secured to the truck bed to partially define a truck box when the tailgate is in a closed position. The check strap assembly includes a member extending from a D-pillar of the truck box to the tailgate and a lock mechanism having a component with an overhang to prevent access to a fastener securing the member to the D-pillar or the tailgate. The D-pillar may include a flange defining an aperture and the member may be a rod having a first end sized for extending through the aperture and a second end with a striker for engagement with a latch mechanism of the tailgate.