The paper

by means of illustrations

demonstrates the necessity of marking definitely design data in drafts

because these design data are the key factors of the embodying the intentions of the designer and the functions of components and parts. In combination with what may occur in practice

the author

as well

puts forward a set of approach that can be used conveniently without complicating the drafts .The approach is used to mark directly design data symbols consisted of signs and codes on the design data elements in drafts and the solution to the of marking of the design data symbols in computer aided drawing. After marking the design data symbols(two or three the symbols only) in drafts

the draft users will know where the design data are at once. Therefore

all kinds of the problems

which arise from the design data not having been marked in drafts

will be solved entirely. Meanwhile it points out when the design data symbols are marked directly on the design data elements of components and parts in drafts

other various problems like the conflicts of many kinds of dimensional tolerances coexisting in a same draft

the disagreement between noted dimensional tolerances and unnoted dimensional tolerances in a same one will be solved effectively.