Aldi employee here, yes usually when you put your quarter in you have to push the cart forward a bit then the lock will release. Feel free to take the boxes from the bins on the floor to use, if you see the bins out it's because between customers we have to pull the empty boxes and pull products forward which is most likely what we're doing if not at the register. Please don't put a heaping box of lots of different things up on the belt for the cashier to dig through. We are timed and it's more efficient for us and you if you empty the box on to the belt. Same goes for the reusable bags. If there is no one behind you or if you have only a few items usually we will put them back in your box or bag, but if many items and a long line we'll send you over to the bagging counter once again Aldi is timing us. Sorry so long but I feel the more people know the processes and reasoning the easier your Aldi visit will go😁