A connection module for housing a contact element used to electrically connect wires within the module, the module being formed of first and second parts arranged to interfit so as to define a first set of openings, each being shaped to receive an end section of one of said wires for electric connection to the contact element, which pass into the module from a first end face toward an opposite second end face, the first part having first and second slots in opposed side walls, and the second part having a first protrusion which is received in a first one of the slots to at least partially fill an open end of said first one of said slots to thereby define an aperture to allow a test probe to access the contact element.