It can sometimes be a real pain for a CT to pass through the long doors if a T sniper is aiming from his spawn like this.
This spot is perfect for a camping sniper as he is pretty much safe from CT rushes from both short and long sides. Also he can escape quickly to B side if he feels himself in danger. Passing through the doors will require quite a skill and experience if the T sniper is a pro himself. Or he may not pass at all if the sniper is really good. I’ll show you a trick where you can blind him and cause him to retreat, so that you can pass through the doors.
While standing in the long tunnel, run forward and hit the flash grenade at the top of the crates as shown below. Remember not to come into sniper’s view while doing this.
The grenade will flash as shown below.
This way you can blind him without getting into his aim.