A minimum of two Markers are required to view models accurately at 1:1 scale in physical space. The simplest way to reliably and repeatedly locate models at 1:1 is using two Markers placed several meters apart using a tape measure. This placement method will be sufficient for quick previews in office environments, or for very small (<4000mm) fabrication tasks. At a larger scale two codes will be insufficient to correct for HoloLens drift.
If precision is not critical then these two markers can alternatively be printed on a single sheet of paper at a known distance apart.