Learning Targets
- Determine which edges are visible from a selected viewing direction.
- Represent blocked features with evenly spaced hidden lines.
- Decide when a hidden line is necessary and when it adds clutter.
IED Unit 1 • Lesson 1.3
Object Lines & Hidden Lines
Focus question: How can a sketch show features that cannot be seen from one view?
Mission Briefing
Today’s Plan
Use this page with the lesson presentation and your engineering notebook.
Success Looks Like
The finished view communicates both the visible shape and the necessary hidden geometry.
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Opening Prompt
When does a feature need to be shown with hidden lines?
Think first, then be ready to share a short response that connects the question to engineering communication.
Reveal: why this matters
A hidden feature should be shown when it is important to understanding the part and cannot be seen directly in the selected view. Unnecessary hidden lines can make a drawing harder to read.
Core Skill
What We Are Practicing
Object lines show visible edges and outlines.
Hidden lines show important internal or blocked features.
Hidden lines should clarify the part rather than fill the view with unnecessary dashes.
Interactive Model
3D Object & Hidden Line Explorer
Study the part in 3D, switch to standard views, and compare the visible edges and hidden features shown in the orthographic drawings.
Loading 3D model…
Drag to rotate • Scroll or pinch to zoom • Arrow keys also rotate
Calculating dimensions…
Reference Drawings
Front, Top, and Right Orthographic Views
Compare each 2D projection with the interactive model. Use the buttons to align the 3D model with the matching standard view.
Study prompt: Which features are visible in the top view but hidden in the front and right views? Explain how the dashed lines help reveal the part’s geometry.
Lesson Interactive
Reveal the Internal Slot
The front surface hides a rectangular slot. Turn on only the two dashed lines needed to communicate the hidden sides of the slot without cluttering the view.
Candidate Hidden Lines
A hidden rectangular slot needs two dashed side edges in this view.
Your Task
Reveal the Features You Cannot See
Use the Lesson 1.3 model to create one view that clearly communicates visible and blocked features.
- Choose the front, top, or right view and list the features directly visible from that direction.
- Rotate the model to locate holes, slots, or edges hidden behind the visible surfaces.
- Draw the selected view with strong object lines and evenly spaced hidden lines.
- Label one hidden-line group with the feature it represents.
Quality check: A reader should be able to infer the hidden feature without seeing the 3D model.
What You Will Submit
Object-Line and Hidden-Line Analysis
Submit one clear view and a brief explanation of your line choices.
Submission standard: Use uniform dash length and spacing; hidden lines should not look like faint object lines.
Resources
Lesson Resources
Lesson 1.3 PowerPoint
Use the lesson slides for guided practice, interactive checks, and the exit ticket.
Introduction to Engineering Design
Return to the IED course hub for units, resources, certifications, and current course information.