Long Throw Bolt Rim Lock back plate

This is an adjustable thickness spacer for the Bolt Long Throw Double Locking Gate Lock Garage Rim Lock  type latch readerly available on eBay and the like. it fits my lock and will likely fit all the others, they aren't made to any great tolerance but will be good enough in the majority of cases. Best way to assess your required thickness is to shove in hole, measure how much sticks out and that's the thickness required.