A housing for a thin active probe has two identical molded housing-halves that when assembled form a cavity that encloses the 
chassis upon which is carried the active circuitry of the probe. The parts exhibit complementary self-symmetry about a longitudinal axis, such that when one is rotated about that axis it performs the 
mating functions needed to 
interlock with another part representing its un-rotated self. 
Interlocking is accomplished by circular tabs and sockets that interfere and prevent the parts from separating once the tabs are in the sockets. The circular tabs are joined to the balance of the housing-half that carries them by a 
narrow neck and can be sprung over the other housing-half to return to their 
natural position and fit into a circular socket in that other housing-half. A tapered edge or ramp portion on the underside of each circular tab allows it to automatically spring out of the way as the two parts are moved toward each other in a direction generally perpendicular to the longitudinal axis of the parts. Each circular socket contains a stop that prevent its tab from completely passing through the socket. Each housing-half has a straight tab between its circular tabs that enter an interior recess on the other housing-half to support its circular sockets as they receive their tabs. Each housing-half contains in a front surface an entire aperture for a detachable probe lead, and each contains in a rear surface at least one half-aperture that, when the two housing-halves are joined, forms a larger aperture whose perimeter engages a corresponding groove in a 
strain relief for a cable. The exterior surface of the mated housing-halves has, on each side through which runs the line of the 
mating edges, a flat shallow recess. The 
interlocking circular tabs and sockets are located within the extent of this shallow recess, which can receive an 
adhesive label that may conceal and stiffen the 
interlocking circular tabs and sockets.