Device for inserting a refractory block into a taphole structure of a metallurgical vessel, in particular a basic oxygen furnace wherein the refractory block is carried by a mounting unit and has a proximate end introducable into the taphole. A distal end with locking elements, which can be coupled to a locking plate of the vessel, is disposed at the outside of the taphole of the vessel. The refractory block can be introduced into the taphole structure until the locking elements of the mounting unit can be attached to and coupled with the coupling head with a manipulator. This mounting unit can be uncoupled with the manipulator, when the refractory block is mortared and fixed in the lining, whereby the mounting unit can be decoupled and removed solely out of the taphole to enable refractory block replacement and gunning of refractory material from the inside of the furnace more easily.