Attach to firewall/motor mount plate and insert into fuselage. Align the post to the angle required and glue firewall in place. The long post allows you to pull the firewall forward for a tight fit in a plane such as a glider that has a tapered nose. It also helps with alignment to be sure the prop/spinner will be centered on the fuselage. Flat side makes it easy to find center and there are graduation marks every 1mm and reference marks at 15, 25, 35, etc.