Refrigerate the can of Carnation milk overnight.
Cut the lemon in half. Use a lemon squeezer and squeeze out the juice. Throw the seeds away. Use a grater and grate the lemon rind.
In a bowl that will withstand boiling water, add Jell-O, sugar, lemon juice, grated lemon rind, and boiling water. Mix with a spoon until the Jell-O is dissolved. Let cool and then refrigerate until it starts to gel.
In the mixer, beat the Carnation milk until it comes to a peak and then add the lemon Jell-O mixture to the beaten Carnation milk. Mix until smooth.
In a small glass cake dish (about 7 x 11) cover the whole bottom with graham cracker crumbs. Pour the whole Jell-O/Carnation milk mixture on top of the graham cracker crumbs. Cover the whole top with more graham cracker crumbs. Refrigerate overnight. The next day, cut and serve.