Another popular form of folk art is banners for societies such as the Orange Order, the Ancient Order of Hibernians, the Apprentice Boys of Derry, and the Royal Black Institution. These are typically painted on silk and are carried in annual parades such as those on Saint Patrick's Day and the Twelfth of July. While wall murals tend to be of mixed artistic quality, banners are usually painted by professionals and are of a high standard. Because marching plays a much bigger role in Northern Irish Protestant culture than Catholic, the majority of banners depict Protestant, unionist or loyalist subjects. Of these the most common is William III of England, whose victory in the Battle of the Boyne is celebrated each year on 12 July. In addition to 'King Billy', Orange Order banners can depict a wide variety of other subjects, including the Crown and Bible; Biblical scenes; scenes from Ulster-related history including the Battle of the Somme; local landmarks; Britannia; and deceased members of the Order. Apprentice Boys' banners typically depict scenes from the Siege of Derry but can also show other unionist topics or deceased members of the organisation. The banners of the Royal Black Institution mostly show Biblical scenes. Catholic banners, also depict a variety of subjects, with Hibernia (the Irish equivalent of Britannia); Saint Patrick; and various nationalist heroes being popular. Trade unions in Northern Ireland sometimes also march with banners.