A manually operated fastener for the side boards of vehicle bodies, comprising: a containment casing in use fixable to a side board of a vehicle body or to another part of the body, the containment casing comprising an inner cavity that is elongate along a main axis of extension and a main opening for accessing the inner cavity made in a first face of the containment casing, parallel to the main axis of extension and which in use is facing towards the outside of the body, and a secondary opening for accessing the inner cavity positioned transversally relative to the first face; an insert slidably inserted in the containment casing, and movable along the main axis of extension between a first position and a second position; at least one first connecting element connected to the insert, movable with it, positioned at the secondary opening, and in use couplable to a second connecting element that is respectively fixed to the other part of the body or to the side board; and a movement unit for moving the insert between the first position and the second position, which is mounted in the containment casing, which is accessible through the main opening and which can be operated manually; wherein when the insert is in the first position the first connecting element is positioned in its own locking position, and when the insert is in the second position the first connecting element is positioned in its own releasing position; characterised: in that the insert comprises at least one first part slidably guided in the containment casing along the main axis of extension, the movement unit being coupled to the first part; in that the first connecting element is movable relative to the first part along a line of translation perpendicular to the main axis of extension, between a back position and a forward position; in that it also comprises thrust means acting on the first connecting element for elastically pushing it towards the back position. a containment casing in use fixable to a side board of a vehicle body or to another part of the body, the containment casing comprising an inner cavity that is elongate along a main axis of extension and a main opening for accessing the inner cavity made in a first face of the containment casing, parallel to the main axis of extension and which in use is facing towards the outside of the body, and a secondary opening for accessing the inner cavity positioned transversally relative to the first face; an insert slidably inserted in the containment casing, and movable along the main axis of extension between a first position and a second position; at least one first connecting element connected to the insert, movable with it, positioned at the secondary opening, and in use couplable to a second connecting element that is respectively fixed to the other part of the body or to the side board; and a movement unit for moving the insert between the first position and the second position, which is mounted in the containment casing, which is accessible through the main opening and which can be operated manually; wherein when the insert is in the first position the first connecting element is positioned in its own locking position, and when the insert is in the second position the first connecting element is positioned in its own releasing position; in that the insert comprises at least one first part slidably guided in the containment casing along the main axis of extension, the movement unit being coupled to the first part; in that the first connecting element is movable relative to the first part along a line of translation perpendicular to the main axis of extension, between a back position and a forward position; in that it also comprises thrust means acting on the first connecting element for elastically pushing it towards the back position.