MLAK stands for Master Locksmiths Access Key.
The key system has been adopted by many organisations, including Councils. They are used in public areas of facilities, often found on gates around accessible Liberty Swings in playgrounds and other areas where people with disabilities can access at any time they wish.
The ACLatch also uses the MLAK for its operation https://www.disabilityaccessconsultants.com.au/access-thru-pool-fences-at-community-facilities/
The keys can only be purchased from the Master Locksmiths Association of Australia and those wishing to get one can only do so with written authority from their doctor, a disability organisation or a community health centre.
Each use of the MLAK locking system is recorded by Spinal Cord Injuries Australia who maintains a register of facilities using the MLAK across Australia.
Further information on MLAK & Toilets can be obtained here: http://www.masterlocksmiths.com.au/mlak.php