How do I crouch?

[Matt]

As title says, how do I crouch?? (keyboard / Xbox controller)
The only thing I was able to google up was this - https://www.youtube.com/watch?v=iJKOwsZGj0I
but again, there's no explanation as to how the guy does it....

[76561198306890551]

You can't. This is just a ground detection glitch where the game isn't sure which surface you are standing on and is alternating between the two.