A device for forming a stack of successively arranged printed sheets has a stack support with support elements and a conveying device supplying printed sheets, arranged in an imbricated arrangement, in a vertical direction to the stack support. The printed sheets formed stacks on the stack support in a stack forming direction and the support elements define a leading end and a trailing end of the stacks. A controllable insertion device correlated with the stack support moves end plates into an intermediate position between the support elements and the leading and trailing ends of the stack, respectively. The insertion device has an insertion member arrangement with passages allowing the support elements to pass through and has a drive for moving the insertion member arrangement perpendicularly to the stack support for inserting the end plates. The insertion device has at least one interstice for receiving end plates.