You will find Cretan barley rusks in any Greek supermarket. As a rule, almost the whole department will be given to them. They are made from barley flour and this is one of the most famous Cretan specialties. Their shelf life is unlimited due to the low moisture content but they are so hard that before use they are usually soaked in water. In other regions of Greece, they are made from a mixture of rye and wheat flour with spices and herbs. If you haven’t found Cretan barley rusks or paximathia then you can take any rye bread and dry it in the oven.