Freehand Sketching
This domain tests rapid, proportionally correct drawing without instruments - the way designers think on paper and explain ideas in a meeting.
Basic technique
Hold the pencil further back and draw from the wrist or shoulder rather than the fingers. Begin with light construction lines: an isometric crate (box) of overall size, centre lines and diagonals. Then commit the final lines as single, confident strokes, allowing a slight overshoot before lifting the pencil. Rotate the paper instead of forcing an awkward direction. Judge proportion by comparing one dimension with another - use the pencil held at arm's length as a measuring stick against the real object or the given views.
Sketching curves
Enclose the circle in a square, mark the four tangent points and the diagonals, then sketch the ellipse through those points. In pictorial sketches, sketch the isometric square first and place the ellipse inside it, remembering that its major axis lies perpendicular to the axis of the cylinder.
Sketching from orthographic views
Build the overall crate, block in the main masses largest first, then add the features in descending order of size. Centre lines and essential hidden detail are still shown in a sketch; freehand does not excuse poor convention.
Worked example
Sketch isometrically a bracket 60 × 40 × 30 mm with a 20 mm diameter hole through the top face. Draw the 60 × 40 isometric crate and bring it to 30 mm height. On the top face, draw the diagonals to locate the hole centre; mark 10 mm out along each axis from that centre to give the four tangent points; sketch the ellipse touching those points, with the major axis running perpendicular to the hole axis.
Traps
Hairy, repeated strokes; sketching too small for detail; getting the overall crate wrong so every feature is out of proportion; shading before the geometry is fixed.