A device for positioning and blocking thin silicon wafers after wire-sawing a silicon wafer block. The device comprises a cassette that accommodates the wafer block and is provided with two contact strips whose sides facing the wafer block encompass elements which engage into narrow cutting gap between the wafers so as to maintain a distance and provide support. This allows the wafers to be fixed in the position thereof even after removing a supporting glass plate such that particularly the gap in the area of the former connecting point to the removed supporting glass plate is maintained and the subsequent singulation process is simplified.