All rules of draughts apply except for capture with a king:
- If a king must make a capture, and the last piece captured is also a king, then the capture must end on the square immediately after the last piece captured.
It means that two kings in the tric trac corners can simply capture a lone king. This so called 'demotion rule' is a wee bit artificial, but then, it presumably helps trimming draughts' embarrassing margin of draws. Whether or not this is the case, in the long run, can be derived from the statistics, which are kept separately for draughts and killer draughts.