I have a sofabed whose back is fixed to the bed by bolt and nut. When I try to loosen the nut by wrench, the bolt and nut move together. There are no rust. How shall I loosen the nut?
Update: the head of bolt has a shallow hex hole. I have got help from another who used hex wrench to stick into the hole of the bolt head and fix/rotate the bolt, together with a regular wrench to rotate the nut.