The vbox component is used to create a vertically oriented box. Added components will be placed underneath each other in a column.

<zk>
    <vbox>    
        <button label="Button 1"/>        
        <button label="Button 2"/>        
    </vbox>    
    <hbox>    
        <button label="Button 3"/>        
        <button label="Button 4"/>        
    </hbox>    
</zk>