Corner taps placed immediately upstream and downstream of the plate; convenient when the plate is provided with an orifice carrier incorporating tappings D and D/2 taps or radius taps placed one pipe diameter upstream and half a pipe diameter downstream of the plate; these can be installed by welding bosses to the pipe Flange taps placed 25.4 mm (1 inch) upstream and downstream of the plate, normally within specialised pipe flanges.