The space configuration illustrated in V?H?W three-plane projection drawing(i.e.front view,top view and left view) can generally be determined completely.However,in some special cases,the uncertainty of the space configuration illustrated in V?H?W three-plane projection drawing is neglected.This paper exemplified that it is very important to pay attention to the uncertainty of the space configuration illustrated in V?H?W three-plane projection drawing, and to avoid the variablility in the engineering design.