one can easily discern what malas are used for in vajrayana buddhism, chanting things like "om mani padme hum", etc. each time you chant it, you go to the next bead. or in pure land, "amituofo" next bead, "amituofo" next bead, "amituofo" next bead, X infinity.
what are they used for though in chan and zen buddhism? mostly what i found searching on line is just people saying that mainly chan and zen don't use them and that when they do it's only a small number of people in sects that have been influenced by vajrayana or pure land. but i see pictures everywhere of chan and zen monks and famous masters wearing or holding malas (modern in photographs and ancient in drawings, paintings and statues) so it seems a little more wide spread than just a few sects or monks influenced by vajrayana or pure land. i can't find anywhere that the practice is explained. all the zen/chan writings i have come accross detail morality, koans, mindfulness, sitting meditation, etc. but i have never come across any that detail or recommend mala practice. i'm puzzled.
could someone tell me how precisely they are used in zen/chan and what specifically is chanted. as much detail as possible please
, such as what schools do what chants, what teachers recommend what types, how to do the chants, etc. etc.