Abstract: An insert 6 is pushed into an eroded tap hole 5 of a steel-making vessel. This insert has outer and inner plates 7 and 8 formed from relatively thin steel sheet or cardboard which will flex so as to adapt itself to the internal dimensions of the tap hole 5 as shown. Between the two plates 7 and 8 there is a tubular support member 9 defining a central passage-way 10 which has holes 11 formed on its side walls which communicate with the open volume 12 between the end plates 7 and 8. A supply hose 13 is connected to the tubular member 10, through which a settable material comprising a clay and binder in wet form is injected so that the whole volume between the end plates 7 and 8 is filled. At the temperatures experienced the clay material will set rapidly so as to block off the tap hole 5.