A system for immobilization of a patient body part for radiotherapy applications includes a device having at least one flanged support member which is mounted to a fixation surface. The device can receive and retain at least two sheets. A first sheet covers the anatomical contours of a first area of a body part. A second sheet covers the anatomical contours of a second area of the body part which is not covered by the first sheet. The system supports the immobilized body part free from the fixation surface by the two sheets and the device.