Abstract: A furnace delining apparatus has a telescopic jib mounted about a horizontal pivot axis on a turntable. The distal end of the jib carries a tool on a carrier swingable about an axis transverse to the jib axis. The carrier is pivotally mounted on a jib extension which can be rotated about its longitudinal axis to selected positions which are defined by locating means on the jib. The extension is permanently mounted for rotation on a spigot projecting axially from the jib and is axially slidable between a position in engagement with the locating means and a free position in which it can be rotated to a new angular position.