Apparatus for precision deploy-attaching beam-mount structure to the outside of an elongate column at plural, defined attachment sites that are distributed and spaced along the length of the column. During use, a column support jig with plural openable/closeable yokes in the apparatus supports a column horizontally for selective rotation about its long axis. A carriage in the apparatus, which holds beam-mount structures to be attached to a supported column, is selectively moveable and position-lockable in defined locations distributed along the supported column between yokes in a pair of spaced yokes to enable precision weld-attaching of the mounts to sides of the column.