Rectangular casing blocks or slices including various functional electronic modules, typically a power slice, a data storage slice, a demountable portable keyboard slice, a demountable communication slice and a demountable visual display slice, are assembled and latched in top-to-bottom attachment or in front-to-back attachment so that a stack of four or mroe slices is formed and the slices are easily removed for off-site use. Each slice has an internal mounting frame to which is attached plastic edge connection strips having interconnection grooves and tongues at opposed ends. The tongues and grooves are slid together and a latch bail provided for latching together strips abutting in a front-to-back attachment. When strips and the frames of the slices to which the strips are to be attached bottom-to-top another series of interfitting tongues and grooves on the ends of the respective strips are slid into aligned abutment and a latch plate pivoted inwardly to lock the strips and slices together. The latch plate also covers and prevents inadvertent disassembly of the bail.