Abstract: An internally threaded split nut having an arcuate gap defining an opening large enough to pass over the outside diameter of a first tubular conduit or elongate rod section from the side, the split nut then being coaxially alignable and threadedly engageable with a cooperatively second threaded conduit or rod section having an outside diameter greater than that of the first section. Use of the subject split nut to releasably secure a water supply valve assembly having a REHAU® hose barb fitting to a wall of an in-wall appliance outlet box is also disclosed.