Union Jack and the Ensign
The union jack is flown on the bow of a ship and the Ensign is flown on the stern of a ship when anchored or moored.
Once underway, the Ensign is flown from the main mast. If the Ensign is flown from the main mast and is half-masted, the union jack is half-masted as well.
The union jack is raised and lowered in the same manner as the Ensign.