The photo's on this page show the recently completed brake gear which is particularly complex on a Bulleid Pacific. Each driving wheel has two brake blocks which clamp onto the wheel directly opposite each other when the brakes are applied.
The photo below shows the brake assembly in position, there are over 50 individual components on this side alone.
The photo above shows the trailing intermediate brake hanger and the brake adjuster assemblies.
The cast iron brake blocks themselves have yet to be purchased. The blocks fit on the block holders, an example of which is indicated.
When the locomotive is in service the brake blocks are replaced periodically as they are worn down and reach scrapping size.