About 1/2 cup fine graham cracker crumbs Dissolve the gelatin in boiling water; add the lemon juice, peel and sugar. Chill until thickened, but still soft. Pour the mixture into a large bowl, add the condensed milk and beat with an electric mixer until smooth and thick. Brush the melted margarine or butter over a 7-by-11-inch pan and coat with soem of the graham cracker crumbs. Pour the lemon mixture into the pan and sprinkle the top with more crumbs. Chill thoroughly before serving.