Abstract: A cage with opposite endwalls and opposite tracks on the latter for circuit panels, of which each track is formed of a pair of resilient leaves arranged side-by-side and bowed toward each other to leave them with adjacent apices intermediate their lengths, with the leaves of the opposite tracks being symmetrical about a median plane, and the leaves of each pair being spaced closest at their apices so that a panel introduced into a pair of tracks has freedom of tilting motion about the apices as a fulcrum for stress-free register of the panel with a groove in a connector block which is more or less in alignment with the tracks.