The Vogon Constructor Fleet was a collaboration of starships created and designed to carry out the action of the one word Vogons loved: demolishion. The ships were also the buildings and structures of the Vogon's homeworld, Planet Vogsphere.
The fleet was under the control of the Galactic Hyperspace Planning Council, a board of directors whose members were Vogons. They voted and discussed the creation of spacelanes.
If a planet needed to be destroyed, the ships of the fleet would surround the entire planet (each covering a certain area). In one second, the planet was disintergrated, not even scratching the bottom of the ship. In the year 2005, the Constructor Fleet destroyed Earth to make way for an interstellar bypass.