The splayed wall forms an angle with the culvert axis, and the water flow is smooth. The wall of the eight-character wall should be built with flaky masonry, and stones or precast concrete blocks can be used when conditions permit.
The figure-eight wall, as its name implies, is two walls shaped like a figure-eight. In culvert construction, it is the two side walls of the entrance and exit of the hole, which is a form of the hole. Ancient buildings should be two eight-character walls at the entrance of ancient big houses or yamen, on which slogans or couplets are usually written.