The prefeeder FLEXYRENGO is an excellent compromise between the automatic feeding, usage simplicity and budget. This machine is particularly suitable where it is necessary a good accessibility of the stack by the operator in order to take out the waste and operate on the cartonboard sheets. The machine can operate completely in automatic. Only the removal of the last sheet under the stack has to be done manually. The prefeeder does not require peculiar format adjustments and it is particularly suitable for short runs.