Keep animals safe and secure in pens, yards, trailers and other enclosures. This auto-locking steel bolt has a hot dipped galvanised finish for outdoor use and long life. It can be mounted inside or outside an enclosure. The bolt cannot be released without the catch underneath being lifted at the same time, making it difficult for animals to open. The catch engages automatically when the bolt is slid home. As an added precaution, a right-angled guard is supplied that can be mounted below the catch opening. This further prevents animals from operating the catch underneath the lock. Two staples or keeps are provided for different applications. A looped one can be used for smaller gates and doors where closure is relatively precise. An additional elongated Harlow keep provides around 80mm up and down movement for larger, looser gates and doors, making it easier to close. It also allows the gate to be raised and lowered slightly when closed.