The tops of tables, sideboards, etc., should not be fixed with screws in the ordinary way. At the front, screws can be driven upwards through the top rail, but at the sides and back, buttons should be employed, as in Fig. 359 , so that the top is free to shrink. It is otherwise liable to split if immovably fixed. The tops of kitchen tables are usually fixed in this way, to allow for shrinkage.