Bank is one of the original maps in Rainbow Six Siege, and it's remained basically the same since launch for one reason: it's really freaking good. Bank has always been pretty competitively viable, even in Pro League, and it's a very unique map that brings its own flavor and intricacies along with it.
Because of this, there are certain things you're going to have to keep in mind specifically when heading into Bank, so let's get into 10 tips for playing here.
10 B LOCKERS/CCTV SITE
Though the Basement site is one of the more viable sites on Bank, there's a lot that needs to be accomplished in the prep phase. There are not two, not three, not even four, but five different ceiling hatches leading either directly into the objective site or an adjacent room. Because of the plethora of entry points into this objective, it's generally a site where Defenders do their best to control the entire floor (besides the Garage). This requires a heavy dose of Anchors in the Basement, with no more than a couple of Roamers free to flank the Attackers wherever needed.
9 1F TELLERS OFFICE/ARCHIVE
This can be a tough site to hold for some teams, simply because it's very difficult to hold any rooms adjacent to the objective. Most Anchors are going to need to stay inside the objective rooms themselves, and even then, there isn't going to be a lot of room to maneuver. Because of the confined space the Anchors are going to be in, they're going to benefit immensely from any and all utility placed inside of the objective.
Generally, Roamers are going to need to have a heavy hand in making some successful plays here, and do as much to keep the Attackers from utilizing vertical play as possible, because the entire ceiling in both objective rooms is destructible.
8 1F STAFF ROOM/OPEN AREA
Despite there being three ceiling hatches to worry about in/near this site, this is usually going to be a bit easier to hold than the previous site. For one, there's a lot of room to maneuver here as an Anchor, making it possible to have quite a few different setups and different spots to hold an angle from. A focal point from the Attackers in the early going is going to be the window inside the 1F Printer Room just beside the 1F Open Area. There are likely going to be Attackers that spawn there and, usually, they'll immediately fire through the window into the objective. Rebuff them there, and they're usually going to try and find a new angle of attack.
Roamers will need to be upstairs to prevent Attackers from feeling too comfortable on the ceiling hatches, allowing the Anchors to focus most of their effort on defending the two double-doors.
7 2F CEO OFFICE/EXECUTIVE LOUNGE
This is usually a pretty interesting site to hold. Early round, there's probably going to be one Attacker outside on the Parking Garage or rappelling at a West window allowing for a sightline into the site from outside. If they're being cheeky, they might fire some stray bullets through any of your door/window barricades, and through any of your soft walls. They probably won't stay up there too long, but if they do, at least take comfort in the fact that they probably aren't helping their team very much.
This objective usually calls for two or three Anchors in the site, holding Attackers at the doorways to allow the Roamers to get off their flank. A Roamers' job here can be pretty tough because keeping control of the hallway just beside the objective for anything longer than the first minute or so of a match is going to be a challenge. The 2F Janitor Closet can be a lifesaver here, just be sure to have a Jager ADS inside or you'll be flashbanged and killed before you have much of a chance to do anything.
6 TWO ENTRANCES WITHOUT MAKING A SOUND
One thing that makes Bank unique is that Attackers have two different entrances into the building that they can use without having to break down a door or bust through a window.
One of these is the Bank Garage entrance on the SW portion of the Basement, and the other is the Tunnel entrance leading from the Sewer. These both give Attackers easy access to both the Server Room Stairs and the Main Stairway.
The other thing that makes Bank unique is the large windows all around the Lobby. There's a parking garage allowing Attackers to get an easy sightline through the windows and into the second floor, and Attackers can simply rappel onto them, as well. There are probably going to be one or two Attackers on these windows in the first minute of the round.
The Lobby can make or break a Defending team, and it all depends on how comfortable they are approaching it. Some teams spend a lot of effort placing one or two Defenders somewhere either in the lobby or on the balcony, and it's possible to have a lot of success rebuffing one or two Attackers here, provided you're capable of staying out of view of those windows. That said, not every team is going to have success playing so heavily in here, and that strategy can do more harm than good.
On a simpler Defense, Defenders can just leave that area alone and focus more on preventing Attackers from exiting the Lobby with any ease.
3 CONTROL STAIRCASES
Because there isn't an overabundance of hallways or rotation paths in Bank (unless you make your own with soft destruction), you probably aren't going to be catching many Attackers off-guard as a Roamer. Attackers are going to usually have a pretty good idea of where to look for Defenders here, so controlling/blocking access to staircases is going make for a much easier time, as opposed to constantly being on the move. Operators like Ela and Lesion are particularly effective at this.
2 CREATIVE CAMERAS
Both Maestro and Valkyrie can get a view of most, if not all of the second floor on Bank very easily. If your team has a reinforcement left, Maestro can place a camera on the reinforced wall on the SW corner of the 2F hallway. If not, he can place it on the white brick portion instead. This Evil Eye has a view of both the North and East portions of the hallway, which is where the majority of the Attackers are going to be for a large portion of the round. Valkyrie can do something similar; her cameras just require a bit more creative tactics to use without being seen.
1 ATTACKER SPAWNS
Lastly, spawns can be a bit frustrating on Bank for an Attacker. Both the Parking Front and the Jewelry Front entrances can be easily spawn-peeked by a Defender immediately as the round starts, so the moment you spawn, it's a good habit to just aim-down-sights directly onto that front door. The Alley Access spawn isn't quite as dangerous, but there are a couple of blind corners that can get you killed if you run by a Defender with a hole in a window or a door.