It is used when installing the cooling system of power transformers, for connecting the power grid that feeds electric motors into a single main line and connecting a cable from an external power grid to it. The body of the trunk box has a cylindrical shape, made of sheet steel. On the wall of the trunk box there are holes in which oil seals are mounted designed to seal the boxes in places where the cable passes through them. On top of the box, with the help of rubber gaskets, they are hermetically sealed with lids. The box has pass-through terminal clips designed for connecting the cable to an external power grid.