Abstract: An enclosure for housing sub-racks carrying circuit boards and modules carrying other electricalcomponents comprises two separately formed identical bodies, each of which constitutes an end wall and a part of each of a pair of oppositely disposed side walls and which are secured together to form an enclosure having two oppositely disposed open faces. Adjacent one of the open faces of the enclosure, means is provided on which sub-racks and modules can be detachably mounted in the enclosure either with the front faces of the sub-racks and modules flush with the open face of the enclosure or with the faces of the sub-racks and modules set back from the open face. Preferably, inner parts of the end walls of the bodies adjacent the other open face of the enclosure are so shaped that sub-racks and modules can be trapped in the enclosure between the inner parts of the end walls when the enclosure is assembled.