"You have to feed lock in from the front because of the two pegs that stop lock being bumped.
This means that you have to remove the turnbuckle. This held by a small, hardened steel roll pin. Despite buying the correct pin punch I was unable to remove this pin. More force would have broken the turnbuckle. The two key slots version is probable OK , but this should be supplied with the turnbuckle loose. Avoid."