When Gillian's house is surrounded by the visiting alien spacecraft, all her kitchen appliances start working, kitchen knives are hurled across the room and the screws holding a ventillator grill in place(inexplicably under a carpet) start to unscrew all by themselves. Look carefully as the screws come out and fall on their sides and you will see a slot has been sawn in the sharp end with a hacksaw so a stage hand can unscrew them from below.