These are very nice to serve with a fish course in place of bread or rolls and a salad. Slice the cucumbers very thin and soak them in ice water for one or two hours. They must be crisp and brittle and made just at serving time. Beat together the olive oil, vinegar, salt and pepper; stand this dressing on the ice until it thickens. Butter thin slices of bread, cover them with a layer of cucumbers that have been drained and dried on a napkin, sprinkle over the dressing, put on another layer of buttered bread. Press together, trim the crusts and cut into triangles. Heap these at once on a napkin and send to the table.