Abstract: Structural formations for mounting an electrical terminal block in an aperture of a panel. A groove is formed on a longitudinal side of a rectangular terminal block. A shoulder with a surface facing toward the panel is formed on the opposite longitudinal side of the terminal block. Coplanar shoulders facing the same direction as the longitudinal shoulder are formed on the ends of the terminal block. The groove has greater width than the thickness of the panel, allowing for the panel to be angled with respect to the groove during insertion. The panel has an aperture with edges that contact the terminal block at all three coplanar shoulders, and the fourth edge contacts the oppositely facing surface of the groove.