The leak devices most frequently used to calibrate leak-detection instruments are permeation leaks. These devices are very sensitive to temperature and can only be used with helium. The physical-leak types that could overcome this limits are prone to clog and their minimum size (about 1 mu m) limits their applicability in the lowest flow range. Here, the authors propose a fabrication technique by means of focused-ion beam with which, in suitable materials, they are able to produce nanometer orifices. These devices [Universitagrave degli Studi di Genova, Italian Patent No., TO2008A000683 (18 September 2008)] work in the molecular-flow regime up to atmospheric pressure and do not clog. Other advantageous characteristics are the possibility of obtaining leak rates in the range equal to those of the permeation type and the linear dependence of the throughput on the inlet pressure.