Noun
topping out (uncountable)
The finishing of a building's roof, often accompanied by a special ceremony.
Topping out and dedication The dedication plaque President Lyndon B. Johnson and Mayor Alfonso J. Cervantes decided on a date for the topping out ceremony, but the arch had not been completed by then. Source: Internet
Topping out in April, 2015, it will be China's second tallest building and the fourth-tallest building in the world when complete (estimated completion by 2020). Source: Internet