25. The cutting methods for sectional views can be divided into five types: full cut, half cut, partial cut, step cut, and combination cut.

26. The annotation of the sectional view includes three parts: ① a symbol representing the position of the cutting plane (cutting line), with letters marked at both ends; ② an arrow indicating the projection direction; ③ the words "x - x" are annotated above the sectional view.

27. Omit all annotated sectional views, indicating that its cutting plane is drawn after being cut through the symmetrical plane of the mechanism.

28. A sectional view is used to express the internal shape of a part, and can be divided into two types: a solid part and a hollow part.

29. The difference between removing a profile and overlapping a profile is: removing a profile - the profile drawn outside the view outline, overlapping a profile - the profile drawn inside the view outline.

30. The graphics in the drawing can only express the structural shape of the part, and the true size of the part should be based on the dimensions marked on the drawing.