USK 1st XV squeezed home by a single point in an epic 32-31 WRU 2 East clash at home to Croesyceiliog on Saturday (October 12), thanks to a late penalty try.
The hosts led 8-0 early on through a try and penalty before a converted Croesey try pulled it back to 8-7.
Usk added a second try for 13-7 before the visitors converted a penalty for 13-10.
The hosts then extended the lead to 20-10 through a converted try, but Croesey hit back with one of their own for 20-17.
It was nip and tuck, with Usk adding another unconverted try for 25-17, before the visitors responded with a converted touch down for 25-24.
And when Croesey went over again with the extras added for 25-31, it looked all over for the hosts until a last gasp penalty try saw Usk take the spoils to go sixth in the table.
High-flying Caldicot came unstuck at mid-table Cwmbran however, going down 20-15 after leading 12-8 at half-time, although they remain second.
Chepstow repeated their previous week's cup win over hosts Oakdale in E3, this time by 32-14, to record their second league win and also go sixth.
Monmouth School's 1st XV, coached by former Wales scrum-hald Richie Rees, lost a 90-point thriller in their last match for four weeks though, just missing out 47-43 at home to Taunton School in the Daily Mail Cup.
Usk visit Garndiffaith on Saturday (October 19), while Chepstow 1sts host Rhymney and their 2nds visit Ynysddu.