You can rotate the menu (change its orientation from horizontal to vertical or vice versa) by pressing the Rotate button on the toolbar or by right-clicking the menu editor and choosing Rotate from the context menu. Obviously, you will not see the effect if your menu consists of only one item - an empty placeholder.

Important note
Rotating a menu with bitmap skin requires that skin to come in both horizontal and vertical versions. If you try to rotate the menu with bitmap skin, which does not have its rotated counterpart, an appropriate warning message will appear.