A terminal block including at least one housing for a connection terminal, the housing extending at least partly within a volume delimited by: a first plane transverse to two side planes delimiting the insulating body, substantially parallel to a general direction joining a first end and a second end of a fastening member, and passing through a connecting area of the fastening member, and a second plane transverse to the two side planes delimiting the insulating body, substantially parallel to the first plane and passing through a connecting area of the rear face, at least a third plane transverse to the two side planes delimiting the insulating body, substantially transverse to the first plane and to the second plane, and passing through the furthest elastic branch of the fastening means intended to interact with an edge of the support rail, and at least a fourth plane transverse to the two side planes delimiting the insulating body, substantially transverse to the first plane and to the second plane, and passing through a retaining member intended to lock a tool.