Match the exact model and supplied hardware before marking the wall.
Sierra and Metropolitan towel warmers have had different mounting hardware across product generations. Earlier documents show cross-head screws, while the attached update drawings show a change to hex-socket hardware. A 6 mm hex-key reference describes the tool; it is not a universal replacement-screw thread specification.
Before installation, identify the full model number and match it to the current instructions. The present dual-connection manuals cover the respective Sierra and Metropolitan -HP models and their mounting/electrical arrangements. Do not use the old hardwired mounting locations for a different model.
Use the dimensions and template for the actual unit, and confirm the mounting centres against its supplied brackets before drilling. The attached red-marked pictures are historical drawing corrections, not a finished universal installation template. Order missing hardware by model and part identification rather than substituting a screw based on appearance.
Sources: Sierra dual-connection installation manual, Metropolitan dual-connection installation manual, and the attached historical hardware update drawings.