I want to remove the towbar from the van I've just bought to increase ground clearance. Done one side, and then discovered these on the other side. Not attempted to do anything with them yet - what's the score? How should they be removed?
To your second question,
Generally, caged nuts would be used during assembly when the location of the Nut is difficult to work with, and especially if the 2 parts prefer to not stay together, which would lead to nuts being dropped. By attaching these first 2 in cages attached to the part, working the Bolt from the other would be much easier until some stability had been brought to the structure being assembled.