I have the same problem and I don't understand the answer. Holding the nut on the opposite side should not be necessary as long as the hex nut actually tightens-- in other words, the spanner holds the opposite side nut in place while you turn the hex nut otherwise they would both turn together, right? This is not necessary, the hex nut tightens just fine. Maybe I am misunderstanding this answer, so please explain further. (I have tightened the hex nut successfully and it always loosens again.) I have the same problem and I don't understand the answer. Holding the nut on the opposite side should not be necessary as long as the hex nut actually tightens-- in other words, the spanner holds the opposite side nut in place while you turn the hex nut otherwise they would both turn together, right? This is not necessary, the hex nut tightens just fine. Maybe I am misunderstanding this answer, so please explain further. (I have tightened the hex nut successfully and it always loosens again.)