Slap the bayan with the whole flat hand — palm and all fingers landing together and staying down — for a heavy, dead stop of sound. Kat is the emphatic member of the closed bass family: bigger and darker than Ka's lighter contact.
It is written where the cycle needs a firm dry accent: Ektaal's "Kat Ta" and Jhap Sawari's khali section are standard sightings. Because it must cut cleanly, the hand cannot bounce — any rebound lets the head hum. Some notations write Ke or Kath for close relatives of the same action.