Indeed, the guide doesn't describe these functions. What file are you trying to modify? Can you perhaps post the code that you're trying to use?

Please note, however, that custom skinning isn't something that we officially support. We have the Skinning portion of the guide for reference, and we may be able to help if it's something simple. However, we will not be able to assist you if it requires more complex coding, or if any problems arise from the use of custom coding. Implementation of custom solutions requires purchasing professional services.

Raphaƫl Lalonde Lefebvre