a latching shoulder which when the latch arm 3 is in the extended position interferes with the bolt 6 and prevents relative movement eg stops the gate from being opened in this embodiment a strong magnet in the retaining member pulls the bolt tip 6 a down to align with the latching shoulder in latching the device 1 operates in a similar manner to the device disclosed in the applicants 39 earlier u s pat no 5 362 116 the device 1 operates as a self latching device which is positively biased to operate by way of a magnetic field when the latch arm 3 and retaining member are axially aligned no manipulation by the user is required for this to occur since latching happens automatically when the retaining member and bolt 6 are axially aligned usually as a result of a closing mechanism moving the gate to the closed position in order to unlatch the device 1 first and second operating mechanisms are provided the first operating mechanism is similar to that disclosed in u s pat no 5 362 116 and comprises a first actuator 9 having an operating handle 10 which is mounted at the top of the elongate housing 2 and connected to the latch arm 3 a user pulls the handle and this causes the latch arm 3 to lift upwardly into the retracted position shown also in fig7 when the alternative operating mechanism is used so that the bolt tip 6 a is removed from the retaining member 7 the gate can then be opened because the handle is positioned at the top of the elongate housing 2.