A stave protection system for a metallurgical furnace, comprising: a stave comprising a plurality of recesses arranged on a front face of the stave; and a plurality of inserts each being received by a respective one of the recesses, the inserts so received projecting from the front face of the stave such that, in use, furnace burden material is trapped by the inserts so as to provide a protective layer of the burden material on the front face of the stave, wherein each insert comprises a set of segments and a retainer which forces the segments against a surface of the respective recess, such that the segments are secured in the recess by frictional contact with the surface of the recess, and wherein: the retainer comprises an inner part and an outer part; at least one of the segments, defining a first subset of the set of segments, is secured in the recess by the inner part; at least one of the segments, defining a second subset of the set of segments, is secured in the recess by only the outer part, so that in use: removal of the outer part of the retainer, by an erosive effect of the burden material thereon, releases the second subset such that burden material may occupy that portion of the recess which is vacated by the second subset; and removal of the inner part of the retainer, by an erosive effect of the burden material thereon, releases the first subset such that burden material may occupy that portion of the recess which is vacated by the first subset, the stave protection system further comprising a locator element which is configured to locate the first subset of the set of segments in the recess, the locator element being configured to support the inner and outer parts (204, 206) of the retainer. a stave comprising a plurality of recesses arranged on a front face of the stave; and a plurality of inserts each being received by a respective one of the recesses, the inserts so received projecting from the front face of the stave such that, in use, furnace burden material is trapped by the inserts so as to provide a protective layer of the burden material on the front face of the stave, wherein each insert comprises a set of segments and a retainer which forces the segments against a surface of the respective recess, such that the segments are secured in the recess by frictional contact with the surface of the recess, and wherein: the retainer comprises an inner part and an outer part; at least one of the segments, defining a first subset of the set of segments, is secured in the recess by the inner part; at least one of the segments, defining a second subset of the set of segments, is secured in the recess by only the outer part, the retainer comprises an inner part and an outer part; at least one of the segments, defining a first subset of the set of segments, is secured in the recess by the inner part; at least one of the segments, defining a second subset of the set of segments, is secured in the recess by only the outer part, so that in use: removal of the outer part of the retainer, by an erosive effect of the burden material thereon, releases the second subset such that burden material may occupy that portion of the recess which is vacated by the second subset; and removal of the inner part of the retainer, by an erosive effect of the burden material thereon, releases the first subset such that burden material may occupy that portion of the recess which is vacated by the first subset, the stave protection system further comprising a locator element which is configured to locate the first subset of the set of segments in the recess, the locator element being configured to support the inner and outer parts (204, 206) of the retainer. removal of the outer part of the retainer, by an erosive effect of the burden material thereon, releases the second subset such that burden material may occupy that portion of the recess which is vacated by the second subset; and removal of the inner part of the retainer, by an erosive effect of the burden material thereon, releases the first subset such that burden material may occupy that portion of the recess which is vacated by the first subset, the stave protection system further comprising a locator element which is configured to locate the first subset of the set of segments in the recess, the locator element being configured to support the inner and outer parts (204, 206) of the retainer.