Eurocard (printed circuit board)
Eurocard is an IEEE standard format for printed circuit board (PCB) cards that can be plugged together into a standard chassis which, in turn, can be mounted in a 19-inch rack. The chassis consists of a series of slotted card guides on the top and bottom, into which the cards are slid so they stand on end, like books on a shelf.
Source: Wikipedia — Eurocard (printed circuit board) (CC BY-SA 4.0)