avaus mahuti katusel, mille kaudu on võimalik läbi viia vedelikutaseme mõõtmist ja proovivõttu, opening in the upper part of the tank to allow the liquid levels in the tank to be measured, opening in the top of a tank through which dipping (gauging) and sampling operations are carried out, ava paagi ülaosas, mille kaudu viiakse läbi sügavuse (vedeliku mahu) mõõtmine ja proovivõtutoimingud, opening in the top of a tank through which gauging and sampling operations may be carried out