Decorative brass trivets by the industrial designer Maurice Ascalon (1913–2003), manufactured by the Pal-Bell Company circa 1940s.
A trivet/ˈtrɪvɨt/ is an object placed between a serving dish or bowl, and a dining table, usually to protect the table from heat or water damage.
Trivet also refers to a tripod used to elevate pots from the coals of an open fire (the word trivet itself ultimately comes from Latin tripes meaning "tripod"). Metal trivets are often tripod-like structures with three legs to support the trivet horizontally in order to hold the dish or pot above the table surface. These are often included with modern non-electric pressure cookers. A trivet may often contain a receptacle for a candle that can be lit to keep food warm.
A three-legged design is optimal because it eliminates wobbling on uneven surfaces.