tee as by waste line 20 as shown in fig3 a retainer ring 21 is fitted on terminal 11 a such fitting may incorporate external threading 22 on 11 a and internal threading 23 on the ring whereby the ring can be tightened toward wall 13 to frictionally position the ring adjacent the wall as shown at 13 b fig4 shows wrench flats 21 d circularly spaced apart on the ring 21 and engageable by a wrench to facilitate such tightening in accordance with an important feature of the invention the preferred ring 21 carries a series of like retention cams 24 spaced apart by gaps 25 and projecting outwardly at circularly spaced positions or intervals about longitudinal axis 27 defined by the ring 21 retention shoulders 29 are defined by the cams at their sides which face wall 13 and are typically angled at angle u03b1 relative to axis 27 as seen in fig1 shoulders 29 face toward wall 13 due to such angling the decorative cover cap 10 which conceals the ring 21 terminal 11 a and threading 22 and 23 is adjustably retained to ring 21 as by a circularly spaced series of holders 30 formed on or carried by.