50 along a line of action with respect to the axes 46 and 62 the interconnectable means 80 comprises interlocking members 82 and 84 on the body member 44 and the connecting member 50 respectively these interlocking members are constructed in a mortise and tenon fashion in the sense that member 82 is received within a dado slot 86 formed in step fashion between the member 84 and a surface 88 of the connecting member 50 the member 82 including a lip 90 spaced from a ledge 92 formed on the body member 44 and the member 84 is received within the space between the lip 90 and the ledge 92 the interlocking member 84 is an arcuate substantially semi circular segment formed about the axis 52 at the port 78 of the connecting member 50 the interlocking member 82 is an annular hub formed about the portal 76 in the body member 44 the center of the annulus being the axis 52 the interlocking members 82 and 84 thus have corresponding surfaces which interface together when the body member 44 and the connecting member 50 are slidably juxtaposed into coupling engagement and may rotate relative to one another when so coupled a peripheral wall 94 of the interlocking member 82 has a conically tapered form the taper being from a recess 46 to the outer surface spaced from the lip inwardly remote from the ledge 92 when the members 82 and 84 are joined the conically tapered portion of the member 82.