Locking member having a male end-piece having a collar, a female end-piece having a ring which receives the male end-piece, and two flaps configured to be pushed in through two apertures of the ring and which are blocked behind the collar following insertion of the male end-piece, each flap having an inner and outer faces connected to each other by front and rear faces, relative to the insertion of the male end-piece. Each flap has inclined portions formed on the front face and set back from a foremost portion of this front face and including a guiding portion connecting the foremost portion to the inner face and cooperating with the end of the male end-piece to guide insertion thereof, and a blocking portion connecting the foremost portion to the front face and blocking the flaps against front edges of the apertures to act counter to opening of the member.