Sift the flour into a mixing bowl and add a pinch of salt. Rub in the margarine and the lard using your hands until the mixture resembles fine crumbs. Add a little cold water (about 1-2 tablespoons per 8oz (225g) of flour) then turn out onto a lightly-floured board or flat surface. Knead it lightly using the heels of your hands and your knuckles, then roll to the desired shape, size, thickness etc.