On page 181 of the Bartitsu Compendium volume II the Finger-press-down Hold described by W. Bruce Sutherland in Ju-Jitsu Self-defence (1916) is reproduced in two variants.
The first is when the defendant has managed to trap the antagonist’s hand with the palm facing towards him. The second is for the case that the defendant has managed to trap the antagonist’s fist with the palm facing upwards (as if the hand had been waved menacingly in front of the protagonist).
The response is the same in both versions. The defendant holds the antagonists hand between both his hands, thumbs facing upwards, fingers reaching around and the palms of the hands pressed towards the side facing him. The thumbs should not be employed in the grip. Then it is just a matter of tilting the antagonist’s hand away/backward to force him onto his knees.
The trick lies in that the defendant can employ all the strength of his shoulders and arms against the strength of the antagonist’s wrist.
The study group first tried this on 2016-10-16.