A removable section of trunking is sealingly coupled to a relatively fixed length of trunking or duct by means of a flexible, preferably elastic, sleeve which is attached to one of the lengths of trunking towards one end thereof and at its other end to a relatively stiff collar which is shaped to fit closely over the adjacent end of the other duct or length of trunking. The elasticity of the sleeve tends to retain the collar in position and to maintain a tight seal whilst permitting a degree of relative movement including longitudinal thermal growth.
