The priest is a light (approx. 150 gr) bat-shaped hand tool of about 30 cm long made of wood, copper or plastic and with or without a widened (diam. approx. 3-4 cm) end (length approx. 6-12 cm) which is often weighted with lead.
With a priest, the angler gives the caught fish a short, hard blow to the head to switch off the brain. This either to kill the fish immediately or to stun it before killing it with another technique, such as slitting its throat, for example.
The handle is also used in the same way on some folding fishing knives. [MOT]