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