Post-it Extreme Notes stay put even in the moist environment of a fridge (left), and the author finds them useful for helping clients learn a new organizational layout (right). Diane Lowy.

Images showing some of the hundreds of thousands of Post-it notes dotted across Hong Kong have been taking social media by storm, amid calls for support and donations of supplies for the protesters.

The app recognizes any size Post-it note so long as they are square (and, indeed, even works with Mac OS Stickies if you photograph your desktop). It’s a free download from iTunes.