The present invention concerns a device and a method for placing and securing sensors/electrodes on the head of an individual. The device/method optimizes signal information and avoids some of the problems connected to the devices and methods in the prior art. The device comprises a rigid, fluid-proof outer layer, an elastic, fluid-proof inner layer with placement points for sensors or electrodes, and a middle layer comprising a fluid between inner and outer layers. The invention also comprises a device for regulating the pressure of the fluid. Inner and outer layers are joined together to form a cavity for receipt of the middle layer.