marypcbuk | I need to borrow a knife sharpener

We have a steel - and a diamond steel - but we have some heavy german knives that just will not take an edge. Before I give up and dump them can anyone lend us one of those fixed blade sharpeners to see if we can get them sharp?

EDIT: becausI want to know if a fixed sharpener will actually work or just be a gadget I pay for and then dump with the knives...