draft drawing; draft plan; preliminary sketch
Used in design, engineering, or planning contexts for a drawing or plan that is still being examined or discussed before finalization.
The designer proposed revisions based on the draft drawing.
In the meeting, they discussed the layout while looking at the draft plan.
下図 is a rough sketch or preliminary drawing, often less formal than 検討図, which implies a stage of examination.
Compound of 検討 (けんとう, 'examination, consideration') and 図 (ず, 'drawing, diagram').