A friend is rebuilding a letterbox after a visit from a car. He wants to know how the plate that contains the access flap is usually mounted. Do you simply put a bit of mortar under it then pack around it, or is it held in place somehow by wires or whatever until it is set?
He was wondering if the weight of the access assembly would make it sink in the mortar as it hardened. I can't see this happening as bricks don't sink (or do they?).