This template is not blank, it adds a little icon in the top-right corner. See?
This template adds your username to Category:Wikipedia checkusers.
Place {{Checkuser topicon}} anywhere on your user page.
This icon is based on {{Top icon}}.
{{Checkuser topicon
| nocat = yes = disables the automatically added category (default = no)
| sortkey = = custom sorting - the relative position of topicons on the page (alphabetical)
}}