A Filling Factory was a munitions factory which specialised in filling various munitions, such as bombs, shells, cartridges, pyrotechnics, screening smokes, etc. In the UK, in both World Wars, the majority of the employees were women. In the UK, in World War I, such a factory belonging to the Ministry of Munitions was known as a National Filling Factory. In the UK, in World War II, such a factory belonging to the Ministry of Supply was known as a Royal Filling Factory (RFF), or a Royal Ordnance Factory (ROF). In terms of organisation, they were part of the Royal Ordnance Factory organisation.