Tsukubo is one of the tools for capturing criminals which was used in the Edo period. It is also one of the three tools along with Sasumata (two-pronged weapon) and Sodegarami (pole weapon with multiple barbed heads).
It is T-shaped and looks very much like shumoku (wooden bell hammer), with its head made of iron. It has a lot of spikes and a long shaft (about two or three meters).
It is used in the same manner as Sodegarami, catching a criminal's clothes and hair and suppressing his/her movement.
At present there are only a few schools that teach an art of using Tsukubo as a weapon.