IMC Welded Duct Connections Down below is really a sample of the Bell sort joint. The male aspect of your joint belongs to the uphill side of the sloping duct so the grease will drain back down. Duct set up requires a very clear distance from combustible supplies. NFPA 96 https://zanewpdvj.blogocial.com/grease-tight-extract-ductwork-can-be-fun-for-anyone-72560847