Convex portion, method of manufacturing convex portion, positioning structure

A convex portion projecting from a plate member, the convex portion comprising:

• a base being part of the plate member,
• a convex body erecting in a cylindrical shape from the base;
• and
• a guide at a top end of the convex body,
• the base including:
• a first inner circumferential surface that is continuous with an inner circumferential surface of the convex body and extends in a direction opposite to an erecting direction of the convex body;
• a second inner circumferential surface that is continuous with the first inner circumferential surface and intersects the erecting direction of the convex body;
• and
• a third inner circumferential surface that is continuous with the second inner circumferential surface and is larger in diameter than the first inner circumferential surface, and the convex body is above the third inner circumferential surface,
• a diameter of an outer circumferential surface of the convex body is equal to a diameter of the third inner circumferential surface.