Abstract: An assembly for thermocouple calibration in a furnace, a furnace and a method of performing thermocouple calibration in a furnace. The assembly comprises a base plate for a furnace process chamber, the base plate comprising a first through hole; a Boat Elevator (BE) cap for the furnace process chamber, the BE cap comprising a second through hole, wherein the base plate and the BE cap are configured such that the first and second through holes are aligned when the base plate and the BE cap are mounted to the furnace process chamber; and a plug structure having a plug element and a mounting plate; wherein the plug structure is configured such that the plug element is removably received in the aligned first and second through holes.