The invention relates to a sealing body, where heat-producing elements of a heating element are contacted from the rear side thereof. Other aspects relate to a sealing body where the site of the heat production and the site of the heat dissipation (i.e. the point of action) are as close to each other as possible. Other aspects relate to a sealing body comprising a heat element with a built-in temperature sensor. Other aspects relate to a sealing body with a defined sealing contour. Other aspects relate to a sealing body having a three-dimensionally structured contact surface. Other aspects relate to a sealing body with a circular, annular, or strip-type heat element. Other aspects relate to a sealing body with built-in electronic circuits. Other aspects relate to a sealing body that can cool the heating element as required. Other aspects relate to a sealing body that can suck up the material to be welded.