Hayatejou 早手錠
(quick handcuffs)
'This is a arresting tool also known as a Hayatejou. Designed to catch and haul off (the prisoner) as depicted in the picture.'
Made from Steel with a chain. One bar is U shaped and the other is round so that they can slot together when not in use (see photo)
A different version of the Hayatejou is mentioned in Fujita Seikos book on hojojutsu....