From AKBAN-wiki, the Martial Arts Database

This unusual blocking action relates to the days of fighting with armor and in Budo Ninjutsu is related mainly to Kukishinden ryu. The block is intended to distance the defender from the enemy while at the same time landing a heavey blow to the only vulnerable inner part of a hand clad in a Japanese Samurai armor.

Using Tai sabaki - Movement and evasion in eight directions to move backwards, and blocking the attack by bringing the fist from below and up in a large circulr motion. the base standing pose for this block is Ichimonji no kamae

Video of the technique

Basic Blocks

Jodan yuke - upper level block

Gedan yuke - lower level block

Broken wing block

Deflection block

Tray block

High block

Low block

Ten chi yuke - all levels blocks

Video of the technique

This technique is part of Budo Ninjutsu Grade requirements syllabus Yellow belt grade requirements, Green belt grade requirements and of Black Belt grade requirements