Corrie ten Boom in 1915
"After more Jews found their way to the Beje, Corrie realized that she needed extra ration cards, the only means by which people in Nazi-occupied countries could buy food. A man named Fred Koornstra kept Corrie supplied with extra radion cards. His developmentally disabled daughter had been attending Corrie's church services for 20 years and he worked in the Food Office, where ration cards were issued. Corrie shared these cards with others who were sheltering Jews and other refugees. Soon the Beje became the center of a network of local Resistance workers.
The Beje became a permanent home for several Jewish refugees and a temporary one for many more (never more than 12 at one time) who would pass through on their way to find a safer hiding place out in the country.
Members of larger Dutch Resistance network heard about the refugee work at the Beje and sent an architect to create a secret room adjacent to Corrie's bedroom, big enough to hide all the refugees living at the Beje at any one time. then an electrician was sent to install a buzzer warning system that would alert everyone to go to the secret room in the event of a Gestapo raid."
From "Corrie ten Boom: Watchmaker, Rescuer, Reconciler" from Women Heroes of World War II: 26 Stories of Espionage, Sabotage, Resistance, and Rescue.