Abstract: Device for fastening built-in wiring equipment, the bottom of the wiring equipment having a fixed projection for engaging behind one L-shaped extension of an inverted hat-profile-shaped support channel, and a movable projection for snapping behind another L-shaped extension thereof, including a support plate having a device integral therewith for mounting a bus bar to hold a circuit breaker and a first L-shaped extension engageable with a projection of the wiring equipment, and a support strip attachable to the support plate and having a second L-shaped extension integral therewith, the first and second extensions forming together an inverted hat-profile-shaped support channel.