It's a distribution block, in a drum/drum setup there is really nothing in there other than the warning light shuttle that will turn your brake warning light on if you lose either the front or the rear brake pressure. I suppose it could be pushed over a bit and partially blocking the port. I have taken them apart and cleaned then out and reused them.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
