If a player is dealt the Krabler (K3) in sequence, that player must automatically bet if checked to, or raise if bet to, one time that round. For example: your board reads X-X-K and you are dealt a 3 on fourth street, and decide not to sell that 3, you must bet or raise one time on that betting round. Similarly, if your board reads X-X-J-3-K, you must also bet or raise once during that betting round. However, if your board were to read X-X-K-J-3, no action would be required since they were not dealt on consecutive streets.
This can be required multiple times for string streets in the instances of K-3-K or 3-K-3.