Pipes, often called bowls, can be made of blown glass, wood, ceramic, stone, or metal. To avoid inhalation of undesirable vapors, certain reactive metals, such as aluminum, are typically not used to make smoking pipes. When speaking about a specific pipe, the term "bowl," "cone piece" or "crater" (the narrowest) often refers to the indentation where cannabis is to be combusted.
Blown-glass pipes are usually intricately and colorfully designed, and can contain materials that change color or become more vivid with repeated use. Such pipes usually have a hole which is covered with a finger during inhalation, and then uncovered to clear the pipe of smoke and cool the burning cannabis. Slang names for this hole include: rush, choke, throttle, carb (short for carburetor), "clear hole" or just "clear", shotgun, and shotty.
Pipes are often assembled with various metal fittings that screw together, with interchangeable, frequently decorative parts. Metal pipes may get hot, because metal is a good conductor of heat; this is avoided by having a crater-diameter narrow enough (such as a 7/32" = 5.5-mm socket wrench) to maintain 385 F/197 C (vaporizing temperature) operation, which protects against wasting THC. (Standard tobacco pipes are usually too wide for cannabis use. Herb for use in a narrow screened crater should be sifted through a 1/16" mesh sieve.) For traditional narrow-gauge utensils which can be used with cannabis, tobacco or any herb, see kiseru (Japan), midwakh (Middle East), sebsi (Morocco).
For a Rastafarian-style longhose chillum, fit a screened socket wrench tightly into a hole at one end of a chillum-shaped (and well decorated) woodpiece, and attach a 20" = 50-cm flexible tube via a hole in the other end. This "whip" (a) lets you see what you're doing as you perform the vape lighting ceremony (keep flame well below crater opening while sucking slow) and (b) gives vapors time to cool on their way to your trachea.
"One-hitter" pipes (many shaped to look like a commercial tobacco cigarette) are small and easily transportable and for legal protection you can carry your drawtube (as described above) in a separate part of your portfolio, ready to assemble at time of use.
Also check out Smokeless Pipes In which smoke cannot escape from the cone piece and therefore all of the herb or plant is completely smoked.