A corner flange connection member configured for joining together adjacent duct channel flanges associated with duct sections includes two leg portions joined together in angular relationship by a corner portion, and at least one opening in said corner portion for receiving at least one fastening member for connecting said corner flange connection member to the duct sections. The at least one opening is shaped so as to threadably receive the fastening member without cutting threads.

There is provided a technique that includes: a first connector including a first opening including two longitudinally extending parallel sides and configured to provide a detachable connection to an opening of a first counterpart; and a second connector including a substantially circular second opening and configured to be connectable to an opening of a second counterpart; and a pipe including an internal space formed in a shape of a polyhedron and configured to allow fluid communication between the first opening and the second opening.