This means that a loose board unites gates and post, running in a slot, and the only way to handle such a gate is to take the loose board by the end and draw it back as far as possible.

Then the gate always swings open of its own accord.

There is a third kind of fastening.

Manuel Cordova used it.

It consists of a padlock and chain and where this is found one had better leave the cursed thing untried for it will never be broken or removed.
By the first shake of the gate and the corresponding rattle Alcatraz knew that the sliding board fastened it.