They are so small, so that you just pass through the items into your shopping cart. Basically you don't have much of an option. If you shop without a shopping cart (like me buying just a few things that fit into my bagpack) the cassier might suggest that I take a cart next time.

Then there is this side-board across the checkout that you can use to bag your purchase.

What you also see a lot in Germany is people taking empty cardboard boxes from the shelves and use them instead of bags at the checkout. It is quick and convenient.