Pedestrians approaching a crosswalk button that has been modified with a silicone fist knew exactly what to do in order to get across the street. Anthropomorphizing a common urban fixture, designer duo Alfredo and Alberto make a walk through Los Angeles a lot more fun with nothing more than some silicone, glue and a #walkbump sticker printed with the simple instructions “fist bump to cross.”

The designers captured video of pedestrians as they encountered the guerrilla installation. Nearly everybody seems game to play along, some snapping selfies. While the Spanish-born designers don’t explain exactly how they made it, all it likely took to create was taking a quick clay mold of the button for a seamless fit, and a separate one of a fist, casting them into one piece in an eye-catching yellow hue.

This ‘quick and dirty’ urban intervention calls to mind the Rotten Apple Project, a series of cheap projects that anyone can replicate in their own cities, from turning a bike rack into a folding seat to screwing coat hooks onto bus stop signs. This kind of active participation in how cities look and function – often without the permission of officials – can enliven public spaces, whether the installations are just for fun or create new uses for existing structures. Check out 12 more creative DIY urban interventions.