Abstract: Pendant superheater or reheater tubes are maintained in spaced relationship by pairs of collar elements joined together in a closely adjacent relationship. One of the collar elements is dimensioned allow for vertical movement of the tube over which it is fitted throughout the range of temperatures to which the tubes are exposed. The other collar is mechanically fixed to the adjacent tube without welding or other means of physically joining in a manner which prevents vertical or rotational movement. The paired collars are physically joined as by welding so that the fixed collar fixes the spacing between tubes and maintains them in the same horizontal plane while allowing for relative vertical movement. As illustrated the fixed collar is locked by being mounted on a curved tube section having a curvature sufficient to prevent relative vertical movement and through interference with the collar wall to prevent relative rotational motion.