The anti-siphon device prevents a hose or siphon tube from being inserted into the fuel inlet line for a fuel tank of a vehicle, such as a tractor-trailer. The cover has a second pitch that is less than the first pitch. The fitting has a hexagonal outside surface portion for grasping and rotating the fitting. A monitor of the tablet PC is fixed on the fixing bracket and the hinge base is fixed on a tablet PC base. When the base plate is installed, the rear end faces a rear portion of the bowl and the front end faces a front portion of the bowl.