Both the 10u and 2u chassis accepted the same circuit cards - the DM chassis takes either 5 or 7 cards (sepending on the age of the unit) and the full size system took up to 12 cards. Only certain slots could contain cards which needed wiring out (like extension/line cards) and other cards like Main or Firmware Processors had to site in single unique slots only. If you got it wrong, you could be very liable to destroy the card or the backpane....

Most cards are hot swappable and can be done live, taking only a few seconds to come back online. Some cards are considered more 'smart' than others with various systems on-board, like make-busy switches, firmware, and ranges of information LEDs and switches.