Cakes should be cooled and the surface should be free from loose crumbs before a filling or frosting is applied, and the filling or frosting should be cool enough so that it will not soak in. Either the top or the bottom crust may be frosted, but the bottom crust is likely to be softer and more level than the top crust. This point should be considered also when fillings are to be put between layers. Fillings usually hold layers together better when the bottom crusts are placed together. A very soft filling should not be used for a cake that is to be kept any considerable time before it is eaten because the filling will soak into the cake and make it soggy. Sometimes the shape of a loaf cake makes it desirable to put the frosting on the bottom crust. The frosting may extend over the top of a cake only or may be spread over the sides. A well-made boiled frosting should be soft, but not soft enough to run. A frosting may be put on with a very smooth surface, may be left rough, or may be scored in ridges or designs.