Please answer a question about the following article about Gymnastics:

A typical pommel horse exercise involves both single leg and double leg work. Single leg skills are generally found in the form of scissors, an element often done on the pommels. Double leg work however, is the main staple of this event. The gymnast swings both legs in a circular motion (clockwise or counterclockwise depending on preference) and performs such skills on all parts of the apparatus. To make the exercise more challenging, gymnasts will often include variations on a typical circling skill by turning (moores and spindles) or by straddling their legs (Flares). Routines end when the gymnast performs a dismount, either by swinging his body over the horse, or landing after a handstand. This requires back muscles to do any sort of skill. From handstands being easy to back or front flips being a little difficult.

What is the main staple of this event?
Double leg work