The #65 leaf piping tip (commonly made by Ateco) is a small, durable, stainless steel nozzle with a V-shaped opening. 

Function: Designed to pipe realistic-looking leaves for floral cake decorations.
Usage: To use it, you hold the tip with the V opening vertical, apply pressure to the piping bag to form the base of the leaf, and slowly release pressure as you pull the tip away, which forms the point and often a center line.