Tjaps or caps (pronounced chops) are an art form in and of themselves.
They are the copper stamps used to apply the wax to the batik fabrics.

The Tjap Making Process

The tjaps are crafted from copper strips.  A lot of time and effort goes into making the tjap before fabric production begins.  It can take days or even weeks to make just one tjap and often more than one is made for a design.

Below are a few videos showing a little bit of the process of tjap making.