Last week at work we had a problem where the carpenter installing medicine cabinets sent a screw through one of our NM cables and caused a short. My apprentice suggested that in lieu of tearing into a lot of sheetrock to re-run the swichtleg to the vanity light, we could just cut into the rock in the one spot where the screw hit, splice the romex there and be done. He said that there was a "UL-approved" splicing device, approved for in-the-wall splices, and that he had personally used one of these devices in the past.

My reading of NEC 300.15 would expressly forbid such a practice and I have never before heard of such an "approved" device. Anyone else?