The guild bank will be used intermittently, with access to it being opened and closed by the Bank Manager in response to current banking projects. Projects will be announced on this site and via the guild message of the day.
A banking project is a guild-wide event which takes place over an extended period of time to accomplish a specific goal. A Burning Crusade based example might be collecting a significant number of Primal Fires and Primal Waters to produce Frost Resist gear for certain raid members. The bank would be opened up to receive the materials from any and all guild members who have them spare, then closed again once the required materials had been collected.
The bank does not store cash for repairs or any materials for training, crafting or enchanting. These are left up to the individual player to store for themselves.