Following on from the Ryōi Shintō-ryū (良移心当流 Sekiguchi-ryū (関口流 柔術) connection. Here are some more illustrations from the:

'Jūjutsu Gokuhi Shinden' (柔術極秘真傳 - The Ultimate Secret of Jūjutsu) written by Hisamatsu Tokinosuke (久松時之助)(First published 1900 (Meiji 33) - reprinted by BABジャパン January 1, 1980).

The pictures show basic Sekiguchi-ryū - Kyūsho (急所) points on the front and back, and a 'Hobaku-ki' (捕縛機), which was an arresting aid used within the Sekiguchi-ryū and a number of other late Edo period Ryūha (including the Kitō-ryū).

It was made of metal and fitted around the palm of the hand. The hook-like spikes that protruded from the Hobaku-ki would have allowed the wearer to take a person into custody, by taking their wrist, and / arm. Once caught, such a person would have been unable to resist, or attempt escape without the spikes digging into them and causing them deep wounds.