Drain tuna and mash with a fork. Stir in mayonnaise and lemon juice. Trim crusts from bread and roll out bread using a rolling pin until it is flattened to about 1/16 inch. Spoon one half of the tuna in a log down the middle of each slice of bread, arrange a carrot stick or half of the shredded carrot in the middle of the tuna and roll up the bread tightly to enclose the filling. Cut each roll crosswise into 4 pieces and arrange cut side up in one layer in a container. Cover tightly. Developed by Sara Moulton for the Grain Foods Foundation. Variation: Spread a little mayonnaise or mustard on the bread. Stack a thin slice of turkey and a thin slice of Swiss cheese on a work surface; place a thin strip of pickle or red bell pepper at one end of the stack and roll the ham and cheese around the pickle. Place the roll on the bread; roll up and proceed as above.