Right of the entrance to the St. Great Martyr George Church in the Voronet
monastery there is Semantron (Romanian: toaca). It's hung on a metal pole, that
is approximately one meter high and most likely to be used to call the nuns to a
mess. It consists of a thick, black metal plate, that gives a loud sound, when
hit with a hammer or something.
Semantron
"The semantron is a percussion instrument used in Eastern, Oriental
Orthodox and Eastern Catholic monasteries to summon the monastics to prayer
or at the start of a procession.
It is also known as a semandron, semanteriom, simantra, xylon and
talanto. In other languages, it is called as follows: Romanian: toaca;
Russian: bilo; Bulgarian, Macedonian, Serbian: klepalo; Arabic: naqus.
[...]
Metal-made
A metal semantron, smaller than those of wood, is usually hung near
the entrance of the catholicon (the monastery's main church). The metal
variety is made of iron or brass (hagiosidera / klepalo); formed of slightly
curved metal plates, these give out a sound not unlike that of a gong."
Source and further information:
en.wikipedia.org/wiki/Semantron