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A Thick line that frames the title block and drawing

Object Line

A think line that shows the visible edges of an object. The most clearly visible line in a drawing.

Hidden line

A thin dashed line that shows an edge not normally visible in a view. Dashes are 1/8" long with spaces of 1/16"

Center Line

A thin line that shows the center points of arcs, circles, and the center of symetrical objects. Short dash is 1/8" and long dash ranges from 1/2" to 1-1/2" in length. Center lines always extend 1/4" Beyond the object they are applied to.

Dimension Line

A thin line with arrowheads at each end, broken in the middle for the dimension

Extension Line

A thin line that extends from the dimension line to the point on the object to which the dimension refers.


A thin, angled line with an arrowhead at one end and a note or dimension at the other. Used to show the exact location of note or dimension

Cutting Plane Line

A think line that shows where an imaginary cutting-plane passes throughan object

Section Line

A thin line used to show the surface cut in a section view. Drawn diagonal on each surface touched by the cutting-plane


Standards or conventions to which drawings are drawn

Cylindrical Surface

A rounded surface forming two curved lines of intersection or circular edges


Small rounded inside corner of an object

Fold Line

A theoretical line between two views where viwing planes fold


To appear shorter to the eye than it actually is

Inclined Plane or Surface

A plane surface that is foreshortened in two principal viewing planes and an edge view in one other principal viewing plane

Normal Surface

A true size of a plane that is parallel to one principal viewing plane and shown as an edge view in other two principal views

Oblique Plane or Surface

A plane or surface that is foreshortened in all three principal viewing planes.


A line or surface at a 90-degree angle to another line

Primary Picture Planes

Front, top, or side reference planes


To turn or twist in order to view a particular surface


Small rounded outside corner of an object

Skew Lines

Non-intersection lines, not parallel to each other or to the principal views

True Size

A surface that is shown in its actual size


Distance from the front to the back plane

First-Angle Projection

All views are projected onto planes located behind the object


Distance form the bottom plane to the top plane


Straight element that is generated by a moving point and has extension only along the path of the point

Line of Sight

Direction from which an object is viewed

Normal Plane

True size plane that is parallel to one principal viewing plane and edge view in other two planes

Orthographic Projeciton

Method of representing the exact shape of an object in two or more views on planes at right angles to each other


A line 90 degrees to a given projection

Projection Lines

Lines which are extended out from the object lines to an adjacent view

Third Angle Projection

All views are projected onto planes lying between the object viewer


To form a mental picture or image


Distance from the left side to the right side of the front or top plane


View that shows the most detail and the fewest hidden lines


Show the height and width dimensions


Shows the Height and depth dimensions


Shows the width and depth dimensions

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