In the USA and Canada a hassock is called a kneeler. In the UK, a kneeler is the long, low bench, or long cushion, located in front of the altar, upon which individuals or groups kneel. It is also the popular term given to people who kneel in a church while praying.
Source: Shorter Oxford English Dictionary: 'Hassock'.
Digital source of illustration (retrieved 22nd June 2016).
GVE