There is a stopper on the back, so you can not push the tubs in to far. You would not want a stopper on the front, because it is very convienent to be able to pull the tubs out for cleaning purposes. You could, however, unstill a pole in the front of all of the tubs that would prevent anyone from opening them. I'm sure it would not be that difficult to figure out a way to lock the pole in place, so that no one was able to open the tubs without your knowledge. Another option is a piece of wood or metal on the front of the rack on hinges. This would also prevent anyone from opening the tubs, and would be easy to lock.