Technical Graphics - The Basics - Line Segments

It is extremely important that you can draw correct and accurate lines in Technical Graphics, so this section covers the basics and a few exercises on drawing straight line segments.

We use the term line segments because in the Drawing community it is accepted that a line continues in both directions to infinity. However we only draw and see a part or section of the line so we call it a line segment. Normally people just refer to a line segment as a line which is quite acceptable but it is always good to know the correct terminology.

Horizontal Line Segments

Horizontal Line Segments are drawn across the page with the T-square firmly secured to the side of the table.

These lines are given their name as the follow the direction of the horizon as we see it between the earth and the sky.

Try and draw, as neatly as possible, seven horizontal line segments of length 75 mm and separated vertically by 10 mm. (Put your mouse over the drawing to the right to see what your answer might look like.)

Vertical Line Segments

Vertical Line Segments are drawn up and down the page with the T-square firmly secured to the side of the table and either the 60°-30° or the 45° degree set square used to draw the line.

Try and draw, as neatly as possible, seven vertical line segments length 75 mm and separated horizontally by 10 mm. (Put your mouse over the image to the right to see what your answer might look like.)

Diagonal Line Segments

Any line segment which is straight but neither Horizontal or Vertical is said to be a Diagonal Line Segment.

If you are asked to draw a diagonal line segment you will be told its angle to the horizontal or vertical. You will usually use one of your set squares or be joining two points.

In the diagram to the right you can see many diagonal line segments.

Here are some important things to remember when Drawing.

  • Keep your instruments very clean.
  • Always have a sharp point on your pencil.
  • Always keep your drawing paper clean and prevent any dirt getting on it.
  • Keep your T-Square tight against the side of the board when you are drawing lines.
  • Always draw lightly until you are sure that the drawing is complete and accurate.
  • Do not rub out construction lines, but do make them neat.
  • Do not make holes through your paper

Exercises

Here are some exercises you can try to improve your drawing of Horizontal, Vertical and Diagonal lines. All three exercises are based on a 60mm X 60mm square which is divided into 36 smaller squares of 10mm X 10mm. Try copying the patterns, or creating your own. You could also colour them in.