Ondol (ON-dol; /ˈɒn.dɒl/, Korean: 온돌; Hanja: 溫突/溫堗; .mw-parser-output .IPA-label-small{font-size:85%}.mw-parser-output .references .IPA-label-small,.mw-parser-output .infobox .IPA-label-small,.mw-parser-output .navbox .IPA-label-small{font-size:100%}Korean pronunciation: [on.dol]) or gudeul (구들; Korean pronunciation: [ku.dɯl]) in Korean traditional architecture is underfloor heating that uses direct heat transfer from wood smoke to heat the underside of a thick masonry floor. In modern usage i Th...