Summary:
Standing inside the skybox puts you in the safezone, making you invincible. You can see from the screenshot that one of the walls of the skybox is below the other, meaning you can stand on top of that wall while still being considered in the safezone. If you look at the chat box in the screenshot you will see that it confirms I am standing inside the safezone. Then you can proceed to snipe and do all sorts of nasty things with impunity.
Able to snipe from top of skybox while invulnerable in idle v21
Details:
Standing inside the skybox puts you in the safezone, making you invincible. You can see from the screenshot that one of the walls of the skybox is below the other, meaning you can stand on top of that wall while still being considered in the safezone. If you look at the chat box in the screenshot you will see that it confirms I am standing inside the safezone. Then you can proceed to snipe and do all sorts of nasty things with impunity.