No weight.
Lets asume there are 2-3 of you doing this together, Bill and Bob.
Bill does 1 rep, hops down, Bob does 1 rep, hops down, Bill does 2 reps, hops down, Bob does 2 reps, hops down, Bill does 3 reps, hops down, Bob only manages 2 reps, next set he starts back at 1, Bill does 4 reps, hops down, Bob does 1 rep, hops down, Bill does 5 reps, Bob does 2 reps, Bill does 1 rep, Bob does 3 reps etc.
My clients get to around 12-14 reps before they fail. Thats over 105 reps. Great finish to a session. The more involved, the more rest you get, the more "rungs" you climb. I have had up to 7 lifters doing it.
as much as I love heavy weights, not sure if you guys noticed, when it comes to chin, I love bodyweight, but doing little things to make it harder.
Some things we do at PTC in regards to chins.
Wide grip chins
Close grip chins
Towell chins
Roman Rings
Ladder chins
Chins with weight
Chins with Mr T
Chin dips....these are nuts and dangerous, 1 arm on the chin bar, one on the dip bar, good luck. Only ever done at PTC, for good reason.
Chins with 2 Rolling Thunder handles
Mixed grip chins
Variation of one arm chin, free hand pulling on wrist, very easy.
Chins with Bands
Chins with chains