Grade 3 · Design & Engineering · Lesson 148

Working Cardboard Door

Build a small cardboard door that opens at least 90 degrees and closes into its frame.

Time2 × 45 minutesTeamsPairs; alternate builder and testerEquipmentBasic classroom design materials; no powered equipment

Your project in view

What you are making

Build a small cardboard door that opens at least 90 degrees and closes into its frame.

This generated example illustrates one possible finished design—not actual student work. Use the lesson’s sizes, connected parts and safety steps; your colors and creative details can be different.

Generated finished-project example for Working Cardboard Door: Build a small cardboard door that opens at least 90 degrees and closes into its frame.
Working Cardboard Door · Generated project example

Student directions · Grade 3

What will you make and do?

Build a small cardboard door that opens at least 90 degrees and closes into its frame.

Teacher overview: Students will plan the specific object described below, make and test a first version, then use their results to improve it. Read one step together, demonstrate the unfamiliar action, and let students complete that step before moving on.

  1. 1Plan your project

    Measure the opening and draw the door with a hinge gap, handle and closing edge.

  2. 2Make the first parts

    Attach the wall to a broad base, then join the door with a flexible tape hinge.

  3. 3Put it together

    Open slowly and find any edge that rubs. Add a simple handle without blocking the frame.

  4. 4Test it fairly

    Open and close ten times. Record rubbing, hinge lifting and successful closes.

  5. 5Improve one part

    Change one hinge gap, tape length or door edge and repeat ten cycles.

  6. 6Show and turn in

    Submit the finished working cardboard door, two labeled ideas and before-and-after evidence. Explain which change the results support.

How will you know it works?

  • Opens at least 90 degrees
  • Closes into the frame for ten cycles
  • Record the stated test and explain one revision

Before you move on

Tell a partner what you are making. Point to the part you will work on next. Draw or dictate your test notes if writing slows you down.

Machine cutting, printer setup and electrical power-on require adult approval. A basic-materials model is a valid way to demonstrate the design when equipment is unavailable.

Keep your plan, test notes and before-and-after evidence with the printable design brief below. Use the detailed teacher plan and any coding guide for tool instructions. These steps continue across the lesson’s meetings, not all in one sitting.

For teachers

Engineering standards

This shows how the lesson connects to the national NGSS engineering standards and what student work you can collect.

Assessed

3-5-ETS1-1

Define the need in Build a small cardboard door that opens at least 90 degrees and closes into its frame. Agree on the two success checks and the listed material limits.

What students show: Two labeled ideas with the target and limits stated.
Practiced

3-5-ETS1-2

Compare the ideas using the project checks: Opens at least 90 degrees; Closes into the frame for ten cycles.

What students show: A selected design with a reason connected to a success check.
Assessed

3-5-ETS1-3

Test, change one feature and retest: Open and close ten times. Record rubbing, hinge lifting and successful closes. Change one hinge gap, tape length or door edge and repeat ten cycles.

What students show: Before-and-after results collected under the same conditions.

Materials

  • Cardboard wall and door
  • paper tape
  • ruler
  • handle tab
  • base card
  • Pencil, planning paper and the printable design brief below

Teacher preparation

  1. Gather per-pair materials: Cardboard wall and door; paper tape; ruler; handle tab; base card.
  2. Make one rough sample and rehearse the exact test: Open and close ten times. Record rubbing, hinge lifting and successful closes.
  3. Set the size, load or distance marks mentioned in the steps before class. Demonstrate an ordinary first attempt, not a perfect model to copy.
  4. Prepare any holes, fasteners or difficult cuts for students. Check the stated safety note and clear the testing space.

Step by step

How to teach it

Meeting 1 · 0–8 min

See the job and plan

  1. Introduce the finished object: Build a small cardboard door that opens at least 90 degrees and closes into its frame.
  2. Measure the opening and draw the door with a hinge gap, handle and closing edge.
  3. Students say what would count as a successful result.
Meeting 1 · 8–18 min

Model the unfamiliar action

  1. Demonstrate slowly: Attach the wall to a broad base, then join the door with a flexible tape hinge.
  2. Pause so partners can repeat the action; provide prepared parts if cutting or folding blocks progress.
Meeting 1 · 18–35 min

Build the first version

  1. Open slowly and find any edge that rubs. Add a simple handle without blocking the frame.
  2. Partners swap builder and checker roles halfway through. Check the working part before decorating.
Meeting 1 · 35–45 min

Try once and save

  1. Run one trial of the stated test to locate an obvious problem. Do not count a changed procedure as a fair comparison.
  2. Label and store the model; sketch its current shape and clear the work area.
Meeting 2 · 0–8 min

Predict and set up

  1. Revisit the two success checks. Agree on identical starting conditions and prepare a before/after results table.
Meeting 2 · 8–23 min

Collect evidence

  1. Open and close ten times. Record rubbing, hinge lifting and successful closes.
  2. One student operates while the other records. Swap for a later trial while noting a change of operator if it affects the result.
Meeting 2 · 23–35 min

Change one thing

  1. Change one hinge gap, tape length or door edge and repeat ten cycles.
  2. Keep the original results rather than replacing them with only the best attempt.
Meeting 2 · 35–45 min

Explain and clean up

  1. Submit the finished working cardboard door, two labeled ideas and before-and-after evidence. Explain which change the results support.
  2. Collect the brief and results; separate reusable materials and clean the test area.

Assessment

  • Opens at least 90 degrees
  • Closes into the frame for ten cycles
  • Student demonstrates the actual task: Open and close ten times. Record rubbing, hinge lifting and successful closes.
  • Record includes failures as well as successes.
  • Student identifies one changed feature and uses the retest to explain the result.

Supports & extensions

  • Provide fold marks or pre-cut parts; accept drawings or dictated observations.
  • Start with the smallest working version of working cardboard door before decoration.
  • Extension after success: choose one more value for the same tested feature, predict its effect and repeat open and close ten times.

Safety & responsible use

  • Teacher checks materials and test conditions before use. Use classroom scissors; adults prepare difficult cuts, holes and fasteners.
  • No powered tools, coding, hot glue or electrical circuits are required. Keep moving objects contained and test loads light.
  • Keep pieces on the tabletop, do not mouth materials and stop if a part tears into a sharp or loose hazard.

No-machine alternative

Use prepared paper parts, larger pieces or an adult-assisted version of the same build. Keep the functional task: Build a small cardboard door that opens at least 90 degrees and closes into its frame. If physical testing is not possible, label sketches as predictions rather than measured results.

Printable student design brief

The challenge

Build a small cardboard door that opens at least 90 degrees and closes into its frame.

Success criteria

  • Opens at least 90 degrees
  • Closes into the frame for ten cycles
  • Record the stated test and explain one revision

Constraints

  • Use only the listed teacher-approved materials
  • Stay within the teacher-set size, load and test-space limits
  • Two 45-minute meetings; keep the first version simple

Engineer’s notes

Who uses this object, and what should it do?
Draw two possible designs. Label the working parts and circle your choice.
Which size, fold, gap or position must you measure or mark?
Before testing, predict what will happen: Open and close ten times. Record rubbing, hinge lifting and successful closes.
Record each trial: condition / expected result / actual result.
Draw the ONE change you made. What stayed the same?
Record the retest. Did the change help, not help, or leave the result uncertain?
Show and explain: one result that supports your conclusion.
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