One of the new quests in Fortnite requires players to mantle five times within five seconds — which, if you know how mantling works, is a bit of a hard thing to accomplish. Not only does this require you to find an area where you can mantle multiple times in a row, but it’ll also require you to time your jumps perfectly so as not to go outside of the time limit.
Thankfully, there are a few different ways you can achieve this, though there’s no guarantee you’ll get it on your first try.
Source: https://www.distractify.com/p/how-to-mantle-fortnite