Mounting hosts and switches
When you're carrying a piece of gear, walk up to a rack, look at a row of empty U slots, and press E to mount it. Hosts and switches rack the exact same way — there's no special procedure for either. If you change your mind later, hold E on a mounted item to un-rack it and carry it off again.
Switches are usually the thinnest things in the rack (often just 1U) and live near the top, so cables can hang down to the hosts below them. Hosts fill in underneath. It's not a rule the game forces on you, but following it keeps your cabling short, tidy, and easy to trace when something breaks.
Detailed explanation
A Rack carries a slot_capacity (12U / 24U / 42U today) and a per-row occupancy map. ItemRacked { kind, entity_id, rack_id, start_u } fires when an entity moves Carried -> mounted. Switches share the rack-U surface with hosts and patch panels; there is no dedicated switch chassis, so a top-of-rack switch is simply a 1U occupant placed high in the same map.
Top-of-rack convention: switches up top, patch panels just below, hosts filling down — this minimizes drop length and keeps the strip readable. The garage wall rack is a real Rack with wall_mount=true, which is why the edd reads as the WALL row in the inspector rather than a free-standing cabinet row.