In some power board is useful to create a track without mask protection to get more thick. For example, this is used in the most of PC power supply (see image http://4.bp.blogspot.com/_eRckBQIzWoY/THSUcWtMHGI/AAAAAAAAAIM/jicGtC2L6Ek/s1600/placa+005.jpg).
How to do it in KiCad? There is some layer or method to put this information and the manufacture house understand?
These might help: