Provisions of shields for protecting welds as well as providing heat treatments are advantageous. Previously such shields were bespoke constructions produced iteratively and empirically for particular applications and uses. By utilization of accurately cut sheets of material within which labyrinths are created it is possible to produce an output flow which is even and incorporates no vortexes. In such circumstances problems with regard to edge entrainment of oxygen causing possible oxidation problems in output flows as well as variations in heat treatments can be avoided. The shield also avoids use of welds which may become distorted during welding or heat treating processes. For reproducibility the shield is formed from accurately produced reproducibility components such that shields can be made at a number of sites to provide the same shield function.