Engineering Drawing Fundamentals: Geometric Shapes and Line Types, Schemes and Mind Maps of Computer Aided Design (CAD)

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TRIANGLES: A triangle is a closed plane figure with three straight sides and their interior angles sum up exactly 1800. The various kinds of triangles: a right triangle, an equilateral triangle, an isosceles triangle, and an obtuse angled triangle

QUADRIALTERAL: It is a plane figure bounded by four straight sides. When opposite sides are parallel, the quadrilateral is also considered to be a parallelogram.

Regular Pentagon

Regular Hexagon

Hidden Lines:  Light, narrow, short, dashed lines.  Shows the outline of a feature that cannot be seen in a particular view.  Used to help clarify a feature, but can be omitted if they clutter a drawing.  Hidden lines should always begin and end with a dash. Exception: When the hidden line begins or ends at a parallel visible or hidden line.  Dashes should join at corners.

Section Lines:  Thin line usually drawn at a 45 degree angle.  Indicates the material that has been cut through in a sectional view.

Dimension Lines:  Thin lines capped on the ends with arrowheads and broken along their length to provide a space for the dimension numeral.  They indicate length.

Extension Lines: Thin lines used to establish the extent of a dimension. Can also be used to show extension of a surface to a theoretical intersection as shown in (b). Begin 1.5mm from the object and extend to 3mm beyond the last dimension. They should not cross dimension lines.