1. Make sure all parts are free from sirt and other crusty stuff. Remove any that you see.
2. Dry fit the parts before ou continue to ensure that they will fit properly.
3. Apply some cleaner to all parts of the fittings and pipes.
4. Apply cement in the same areas you applied the cleaner.
5. Glue the cleanout adapter to one end of the compbustion chamber (the short, fat piece of piping)
6. On the other side of the combustion chamber, glue on the 4" to 2" reducer.
7. Take the longer piece of piping, and glue one one end of it to the 2" part of the reducer.
8. Drill two holes at either side of the combustion chamber for the drywall screws, slightly smaller that the screw itself.
9. After you have the drywall screws screwed in, either solder (recommended) or tape the lead from the BBQ ignitor to one of the drywall screws.
10. Let the glue dry out for at least 24 hours.
11. Open the cleanout plug and test fire the ignition system by pressing down the red button. Make sure that your glue is completely dried, and that no fumes stil linger within.If you see a blue spark fly across the two drywall screws, you've done it right.