https://www.polygon.com/2018/8/22/17767868/fortnite-update-rifts-patch

Epic Games likes to tease items coming to Fortnite by showing them off in the informational screen that pops up when you first log into the game, and right now that screen is showing off a new item called the Rift-To-Go. Imagine the rifts that currently allow you to teleport above your location on the map, but carried in your pocket and deployed on command.

The static rifts, one of which is shown at the top of this post, appeared in the game at the beginning of season five. Players learned that they could jump to an area above their current position by walking through them, which allowed them to either get the drop on other players or to drift away from the current battle. The distinctive sound of a rift in use also lets you know when you might want to look up to see players falling back into the fight.