Hi, welcome to the forum, not sure what vehicle your putting this to , but all Dormobiles should be the same, at the ends of the poles, you will find a couple of rivits on the side of the pole about one inch from the end. This will also appear to be rivited through the material and holding a plastic ‘lug’.
The rivets need to be drilled out, ove this is done the ends of the bracket pull out from the pole, releasing the material.
Sorry if that does not make sense.
John