It's always best to check with the guild master or offices for things like that as it will vary between guilds and may not be obvious from the permissions you have.

One of my guilds says the bank is a free for all, anyone can take as much or as little as they like from it and they're willing to take the risk that someone might take the lot (not that it's a big risk, there's nothing that valuable or useful in there). Another guild has it open to members who aren't brand new but asks that you only take what you need and up to a limit of 10 items per day (there is no way to enforce this, other than asking people to respect the rule and each other) and to, sooner or later, repay it by dropping in items you don't need. My third guild restricts withdrawals to officers but anyone can have any item/s they want - they just have to ask rather than being trusted not to abuse the system.