1 – The desired text; can contain wikilinks ([[]]). You can escape the equals sign either by using {{=}} or by explicitly mentioning the 1= parameter.
nb – Give any non-empty value in order to apply a {{nobold}} template to the text.
va – Vertical alignment (bottom, top, middle). Default is bottom.
stp – Give any non-empty value in order to apply a top padding to the cell (useful if the header is bottom-aligned; required for sortable columns).
mw – Manual width; override the default value, which was automatically generated based on the number of line breaks (you can use <br>, <BR /> or any other combination).
style – Additional styles for the <div/> containing the rotated text. May contain double quotes.
cellstyle – Additional styles for the entire cell. May contain double quotes. Use this instead of the cell's style attribute. Use background-color instead of background if you need it for the header of a sortable column.
! {{vertical header|Your text here}} – basic example
! {{vertical header|nb=1|stp=1|Your text here}} – produces an explicitly sortable, no-bold, sortable header
! {{vertical header|va=top|Your text here}} – produces an unsortable, top-aligned table header
! colspan="2" {{vertical header|cellstyle=background-color:gold|Your text here}} – produces an unsortable header spanning two columns, with a gold background; use no vertical bar after colspan
An example below (from Help:Sorting) with headers that span rows or columns (using rowspan and colspan). Note that there is no vertical bar | between rowspan=2 and {{vert header...}}