Apple Video System - Manual (Page 21)

14 Slip the three tabs at the top of the back panel into the
matching grooves in the computer case.
15 Snap the bottom of the panel into place, making sure it is
flush with the back of the computer.
Snap the plastic back panel into place.
Slip the three tabs on the
back panel into the grooves
in the computer case.
15 Installing the Card and Software and Connecting Video Equipment