What do you do with valuables such as laptops if you do end up bringing them with you? Are there lockboxes?
Be careful, if the adelaide is overbooked and they transfer you to Dakota Hotel, most lockers in the room I was in there were broken.
There is a huge box under your bed. Its just the compartment under the bed. As everybody said you have to bring your own locker. The compartment is big enough to even store a whole suitcase.
under each lower bed, there is a small chamber where you can instore youe stuff, just bring a lock. also, maybe you can ask the front desk if they have more lockers
The locker under your bed should be secure enough. Bring a small-medium sized pad lock or you can purchase one at the reception. If you need to store your luggage after you check out, they do put it in a locked collective storage. But on the other hand, there is no identification system so anybody could claim that your luggage is theirs.
Get an answer from Adelaide Hostel staff and past guests.