In construction and function, a bong is similar to a hookah, except smaller and especially more portable. A bong may be constructed from any air- and water-tight vessel by adding a bowl and stem apparatus (or slide) which guides air downward to below water level whence it bubbles upward ("bubbler") during use. To get fresh air into the bong and harvest the last remaining smoke, a hole known as the "carburetor", "carb", "choke", "bink", "rush", "shotty", "kick hole", or simply "hole", somewhere on the lower part of the bong above water level, is first kept covered during the smoking process, then opened to allow the smoke to be drawn into the respiratory system. On bongs without such a hole, the bowl and/or the stem are removed to allow air from the hole that holds the stem.