English Cathedrals - Knocker, Durham Cathedral - Fabulous Monster door Knocker. Part of Box 144 Boswell Collection - English Cathedrals. The Sanctuary Knocker or hagoday is an ornamental knocker on the door of a cathedral. Under medieval English common law, these instruments supposedly afforded the right of asylum to anybody who touched them. Examples of Sanctuary Knockers can be found on Durham Cathedral,( the St. Nicholas church in Gloucester and the Church of the Holy Trinity, Stratford-upon-Avon) . By 1623, the laws permitting church sanctuary had been overturned by parliament.