A universal nipple for securement of a wall-mountable structure to a mounting surface is provided. The nipple includes a shank having an elongate body of predefined length that terminates in opposed proximate and distal ends. The proximate end has an enlarged head portion through which an opening is defined, and the distal end has engagement means defined thereat for engagement with the mounting surface. The body has a generally circumferential outer surface and an inner surface defining a tapering lumen that is coextensive with the proximate and distal ends. The engagement means comprises at least one, and preferably plural, series of threads defined along the outer circumferential surface with grooves distributed intermittently therebetween. The body is easily truncated along a selective groove so as to accommodate mounting surfaces of varying thicknesses and establish fluid communication between a wall-mountable fluid delivery device and plumbing structure provided at or adjacent the mounting surface.