Nobody types in how many units a server takes. Commissioning reads the SMBIOS chassis height; without one the model decides, from a table of heights checked against vendor documentation (Dell, HPE, Lenovo, xFusion, Fujitsu, Inspur/KAYTUS, GIGABYTE; Supermicro model numbers do not carry the height), and rack_units in config.json covers the rest and overrides both. Sleds of a multi-node chassis share its units. NetBox device types get the height (0 for sleds, which go into the rack without a position; Rollcall's own types are corrected). The rack elevation spans each server over its height, draws a chassis's sleds as one block, marks unknown heights and lists overlaps. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>