Here are some key things students should remember when using hidden lines in technical drawings:

• What Hidden Lines Show

• Hidden lines show edges you can't see - like features behind or inside an object

• They represent real edges that are blocked from view

• Think of them as "x-ray vision" lines that show what's behind surfaces

2. How to Draw Hidden Lines

• Use evenly spaced dashes (each dash should be about the same length)

• Make the dashes lighter than object lines but dark enough to see clearly

• Keep spaces between dashes consistent

• Use a ruler or straight edge - dashes should follow a straight line

3. Important Rules

• Hidden lines should be narrower than object lines

• Start and end hidden lines with dashes, not spaces

• When hidden lines meet other lines, try to end with a dash at the intersection

• Don't overuse hidden lines - sometimes another view is better

4. Common Mistakes to Avoid

• Don't make dashes random lengths or spacing

• Don't make hidden lines as bold as object lines

• Don't use hidden lines for features that could be shown in another view

• Avoid using hidden lines when a section view would be clearer

5. Line Priority

• Hidden lines should be less visible than object lines

• If a hidden line crosses a center line, the hidden line should be continuous

• Hidden lines can be broken at intersections with object lines

Practice Challenge

With a group, students will build a simple structure out of linking cubes and help each other draw multiple views that include hidden lines.  If the structure does not require hidden lines in the drawing, draw a different view that does or rebuild.

Reflection

"Why do we need to show hidden lines in our drawings?"

"What might happen if you forgot to include hidden lines in your drawing?"

"When might it be better to use a different view instead of hidden lines?