Flake the salmon. Add to it the salt, cayenne and cucumber, grated and drained. Just before serving time butter the bread, cut it into thin slices, put over the top a layer of the flaked fish, then a thin layer of mayonnaise or sandwich dressing and another covering of bread. Press together, trim the crusts and cut directly across the slice, making two long sandwiches about an inch and a half to two inches wide.