All Octicons
checkbox-fill
Octicon sizes navigation
React
import {CheckboxFillIcon} from '@primer/octicons-react' <CheckboxFillIcon size={24} />
Rails
<%= render(Primer::Beta::Octicon.new(:"checkbox-fill", size: :medium)) %>
Jekyll
{% octicon checkbox-fill height:24 %}
Figma
This icon is called checkbox-fill-24 in Primer's Octicons library.