The Pailbat is one of the weapons that the Gropagas are most often instructed to use to capture runaway prisoners. It is basically a bat with a bucket attached at the top end of it with the the handle of the bucket linked at the bat.
It seems likely that the Pailbat is used to capture runaways because of the simple genious of using a pail and a bat together allows a Gropaga to take down and then stop a fleeing opponent. The pailbat can first be used to beat the quarry, as shown in the source, then the pail itself might be used as a way of suddenly stoping them by bringing the pail down on their head rather like a lasso. This would cover their vision and stop them from getting any farther away, then it could be used to pull them to the ground where they can be recaptured.
The pail is just large enough to contain Wozealso cakes to throw at enemies.