Folding machines are machines used for folding, usually paper. There are around three types of folding machines, buckle folders, knife folders and a combination of these two types of folding machines. The knife folding machines work by striking the paper with a knife between two rollers. The knife is not sharp; it simply hits the paper where the fold is desired. Buckle folding machines work by feeding the paper at high speeds until it hits a stop, and the paper buckles. Folding machines use two types of feeding systems. One is flat pile, where the paper is placed on a feeding table, and the second type of feeder used by a folding machine is called, round pile, and involves the sheets of paper being placed onto a belt or rollers.