The knife (10) has housing (11) that comprises a first housing unit (12) and a second housing unit (13). The second housing unit is movable relative to first housing unit on movement path between open and closed positions. The first and second locking units are associated with first and second housing units respectively. The first locking unit is provided with an arm (28) which is movable between locking and releasing positions. The arm is provided with a locking surface (30) that is releasably moved into movement path of a holding surface (31) of second locking unit.
