42 just above the base 14 a central opening 44 is formed in the body 12 between the recesses 40 and 42 and a lateral bore 46 communicates the central opening 44 with the recess 42 as shown a detent member 48 is slideably located in the bore 46 and is formed with a flange portion 50 which abuts the edge of the opening 44 adjacent the bore 46 and has a shaft portion 52 which projects through the bore 46 and extends some distance into the recess 42 a spring 54 is located within the opening 44 of the body 12 and serves to urge the detent member 48 into position in use the terminal block 12 is secured between a pair of opposed spaced apart flanges or rails as seen at 56 and 58 in fig1 and 13 the flanges 56 and 58 may be supported by a generally u shaped channel member as shown in applicant 39 s earlier patent however the details of the support of the flanges 56 and 58 is not pertinent to the present invention in order to secure the terminal block 12 to the flanges 56 and 58 the block 12 is tilted as seen in fig1 and the end.