27). 20. Using a suitable bit (e.g. 2mm), drill through the extension and outlet. Secure using two of the screws supplied. 21. The remaining screw must be used to secure the adaptor to the concentric terminal. 22. When the plume outlet is positioned under a balcony or other projection (Fig. 28) it must protrude at least 200mm (it is not necessary to extend it further than this). 23. When under balconies or projections it is permissible to rotate the concentric flue length up to 70°, clockwise or