No it just slots into the hole, the weight of the chimney pipes and the support brackets on the wall hold it. That support plate threw me too just doesnt look right because it goes upside down for the cleanout and there's nothing really locking into place .. seems wierd but its right.
Just curious why couldn't you install thimble right above woodstove, where you have it sitting. Why the extra elbow and pipe. Shop must be toasty now. I installed a furnace in my garage. And I'm up in the air about going through roof or wall. That selkirk shit is expensive. Thanks for the video