Letter folding machine is a machine that you can use to fold paper with letter size. These machine are typically used for creating letter folds and accordion folds, other can have more fold types such as half or fold-out with the same size, the letter size.
In office use, this machine is very useful. You can make thousand letter to customers in minutes. As an example, bank will make an invoice for credit cards, the letter size paper of invoices that need to folded to make it fit into envelopes. Everyday thousand invoices need to folded, it's impossible if do it with your hand, so you need a machine called letter folding machine.
Letter folding machine is easy to find, just visit machinery supplies near you.